whey protein isolates ( wpi ) can be obtained from commercial - scale fractionation of cheese whey by various processes , including ion - exchange processing using cationic and / or anionic resins selected for the intended functionality of the isolate . ( pearce , r . j ., 1992 , whey protein recovery and whey protein fractionation , whey and lactose processing , j g zadow , ed ., elsevier , london , 271 - 316 .) commercial wpi products issued from ion - exchange processing , such as bipro ™ ( davisco foods international , inc ., lesueur , minn . ), are characterized by a high protein content (& gt ; 94 % w / w ), low ash content (& lt ; 3 %), traces (& lt ; 1 %) of fat and lactose . the protein distribution of a typical wpi shows 55 - 65 % β - lactoglobulin , 17 - 25 % α - lactalbumin , 4 - 7 % bovine serum albumin , 7 - 11 % immunoglobulins and less than 1 % others . bipro ™ whey protein isolate is the preferred source of whey protein isolate for use in the invention and is available from davisco foods international , inc ., with offices at 11000 w . 78th street , suite 210 , eden prairie , minn . 55344 . the preferred bipro ™ whey protein isolate has a ( pdcaas ) protein digestibility corrected amino acid score of 1 . 14 . the fat and lactose levels are less than 1 %. the bipro ™ whey protein isolate is prepared by ion - exchange technology , and contains about 55 - 65 % ( w / w ) β - lactoglobulin . preferaby , the whey protein isolate employed according to the invention will contain at least 55 % and preferably at least 60 % β - lactoglobulin , with the remaining comprising α - lactalbumin , serum albumin and immunoglobulins in the above ranges . bipro ™ is essentially undenatured and is fully soluble over the ph range 2 . 0 to 9 . 0 , and has the following analysis : * all results reported “ as is ” basis except where noted . standard methods for the examination of dairy products , 16th edition . as noted , whey protein isolates other than bipro ™ can be employed and where used preferably have similar analyses to that above , varying by from 0 to 25 %, e . g . from 5 to 10 %, or less , from the above typical range values . a suitable whey protein isolate can be produced having similar properties through a selective ion exchange process that selects the primary functional proteins — beta — lactoglobulin and alpha — lactalbumin — for concentration and spray drying . such a process is described in u . s . pat . no . 4 , 154 , 675 to jowett , et al ., and u . s . pat . no . 4 , 218 , 490 to phillips , et al . if properly produced , whey protein fractions having lower protein contents , e . g ., as low as 35 %, might be employed . in addition , β - lg produced by ion exchange separation can also be employed , but is less preferred than the bipro ™ whey protein isolate . on a more detailed analysis of bipro ™ whey protein isolate , the following is found or each 100 grams of whey protein isolate : and , to provide an amino acid profile of the preferred bipro ™ whey protein isolate , samples were subjected to drying for 24 hours in a dessicator over phosphorus pentoxide and sodium hydroxide . the dry samples were hydrolyzed in hcl vapor ( 6n hcl with 1 % phenol and 0 . 5 % sodium sulfite ) under argon atmosphere . after 20 hours of hydrolysis at 110 degrees celsius , the samples were dissolved in 200 μl of beckman na - s sample buffer . this acid hydrolysis method destroys tryptophan . analyses were conducted on a beckman 6300 amino acid analyzer . norleucine was used as an internal standard . the analysis showed the following : again , when whey protein isolates other than bipro ™ are employed , they preferably have similar analyses to that above , varying by from 0 to 25 %, e . g ., from 5 - 10 %, or less , from the above values . enzymatic digests of bipro ™ whey protein isolate were prepared using animal , bacterial and fungal proteases , in order to determine the potential of these commercial substrates for the preparation of peptide mixtures having antihypertensive activities . the main objective of the present study was to investigate the antihypertensive effect of some specific whey protein hydrolysates . the following summarizes experiments that have been carried out in conscious spontaneously hypertensive rats ( shr ) to characterize the antihypertensive effect and establish the dose response curve for each hydrolysate . the shr are considered as a genetic model of essential hypertension and are currently used to understand the development and establishment of hypertension and to determine the blood pressure lowering effect of newly synthesized antihypertensive drugs . moreover , in a previous study carried out in shr , we found that the intravenous injection of an angiotensin i - coverting enzyme ( ace ) inhibitor , captopril , caused a marked reduction in blood pressure accompanied by significant vasodilations in renal , superior mesenteric and hindquarter vascular beds ( unpublished data ). therefore , the shr appears to be very reactive to ace inhibition and then should provide us with very useful information in determining if specific whey protein hydrolysates exhibit a significant antihypertensive property . three whey protein hydrolysates ( namely , 601 , 603k and 605k ) and controls phosphate buffered saline ( pbs ) and untreated bipro ™ whey protein isolate , have been examined . the effects of each whey protein on mean and phasic arterial blood pressure and heart rate have been investigated in conscious unrestrained male shr . in the present study , the animals were chronically instrumented with one intravascular catheter implanted in the left femoral artery to permit a continuous recording of blood pressure and heart rate . this technique is very well developed in our laboratory and is routinely performed ( bachelard , h . and g . drolet , cardiovascular responses to paraventricular ( pvn ) injections of opioid agonists in conscious rats , abstract society for neuroscience . 18 : 1175 , 1992 ; bachelard , h . and m . pitre , regional haemodynarnic effects of μ -, δ -, κ - opioid agonists microinjected into the hypothalamic paraventricular nuclei of conscious , unrestrained rats , br . j . pharmacol , 115 : 613 - 621 , 1995 ; pitre , m ., h . gaudreault , m . santure , a . nadeau , and h . bachelard . isradipine and insulin sensitivity in hypertensive rats , am . j physiol ., 39 : e1038 - e1048 , 1999 ; pitre , m ., a . nateau and h . bachelard , insulin sensitivity and hemodynamic responses to insulin in wistar - kyoto and spontaneously hypertensive rats , am . j physiol . 271 : e658 - e668 , 1996 ). this experimental approach constitutes a powerful tool to investigate the hemodynamic responses to whey proteins in conscious rats . the non - invasive technique currently used by others to measure systolic blood pressure , the tail cuff sphygmomanometer , is stressfull for the animal , ( the rat has to be immobilized in a restrainer during measurement ), and is subject to a large variability . therefore , considering the inherent variability in blood pressure measurements in conscious animals , and that the shr rats are known to be very reactive to stressful stimuli , we believed that there is some incertitude in measurements made with the tail cuff technique , particularly in establishing a steady baseline measurement . in contrast , by directly and continuously recording blood pressure , it is easier to take into account this variability and make more reliable blood pressure measurements . moreover , our rats were well adapted to the system for a few days prior to the experiments , and direct measurement of blood pressure was made without causing any pain or stress to the animal . therefore , the direct and continuous recording of blood pressure and heart rate in conscious , unrestrained animals represent a clear advantage over the other non - invasive technique . whey protein isolate ( bipro ™) was obtained from davisco foods international ( le sueur , minn ., usa ). hepes sodium salt , hippuryl - l - histidyl - l - leucine , and angiotensin converting enzyme ( from rabbit lung ) were purchased from sigma chemical co . ( st . louis , usa ). all other products used were analytical grade . whey proteins ( bipro ™) were solubilized at 20 % w / v , adjusted to ph 8 . 0 or 8 . 5 by using a mixture of naoh and koh 4n and maintained at temperatures between 40 ° c . and 50 ° c . corresponding to the optimal temperature of the enzymes used . table 1 reports the characteristics of the enzymes used for the preparation of the enzymatic hydrolysates for the study . bipro ™ whey protein isolate was utilized for the preparation of 601 , 603k and 605k . the protein solutions were incubated with the proteases at an enzyme : substrate ratio of 1 : 800 for 601 , 1 : 50 for 603k and 1 : 100 for 605k . the enzymatic hydrolysis was performed under ph - stat conditions until a degree of hydrolysis ( dh ) of 4 . 5 - 6 . 5 % for 601 and under a combination of ph - stat and osmometry methods until a dh of 7 . 0 - 10 . 0 % for 603k , and a dh of 13 . 0 - 17 . 0 % for 605k . the hydrolysis reaction was stopped at the selected dh values by means of heat treatment ( 75 to 85 ° c . for 15 s ) in a plate heat exchanger to inactivate the enzyme and followed by cooling and storage at 5 - 10 ° c . until further processing . the resulting hydrolysates were further spray dried and handled as powdered ingredient . fractions can be taken based on molecular weight and tested for relative activity , with the most active fractions selected . a typical analysis for the 601k and 603k products prepared from bipro ™ whey protein hydrolysate are given below . all surgical and experimental procedures followed institutional animal care guidelines . male shr rats ( aged 20 to 24 weeks and weighing 300 - 350 g ) were purchased from charles river canada . the rats were anesthetized with a mixture of ketamine - xylazine ( 100 and 10 mg kg − 1 ), respectively , i . p ., supplemented as required ) and one catheter was implanted in the distal abdominal aorta via the left femoral artery ( for measurement of blood pressure and heart rate ). then , the catheter was tunneled subcutaneously to emerge at the back of the neck and was passed through a flexible , protecting spring attached to a custom - made harness worn by the rat . the rats were given s . c . injections of ampicillin ( 150 mg kg − 1 ) and anafen ( 5mg kg − 1 ) and returned to their home cages . experiments began at least 4 days after this surgical step . throughout the experiments , three variables were recorded ( heart rate and phasic and mean arterial blood pressure ) using a biopac data acquisition and analysis system ( model mp 100 , acqkowledge software version 3 . 1 ). at selected time points heart rate , phasic and mean arterial blood pressure were measured , to represent the full profile of the effects of the hydrolysates or bipro whey protein isolate , and related to the pre - treatment baseline value . the rats were conscious , unrestrained and were allowed free access to water and food for the duration of the experiment . the cardiovascular changes elicited by oral administration of bipro whey protein isolate or specific whey protein hydrolysates ( 601 , 603k , 605k ) have been evaluated in conscious , unrestrained shr . the rats were used on four consecutive days , during which they received increasing doses of only one specific hydrolysate ( 601 , 603k , 605k ) or the bipro by gastric intubation . the lyophilized whey protein hydrolysate powder was dissolved in 0 . 2 mm pbs ( ph 7 . 2 ) ( the same vehicle , 0 . 2 mm pbs , was used for control administrations ) and was given in a volume of 0 . 5 ml . all solutions were freshly prepared . thus , on a typical day , soon after basal measurements of blood pressure and heart rate , the rats were given the vehicle ( control pbs on day 1 ) or an isolated dose of a specific hydrolysate ( 30 mg / kg on day 2 , 75 mg / kg on day 3 and 150 mglkg on day 4 ) or bipro whey protein isolate ( 30 mg / kg on day 2 , 75 mg / kg on day 3 and 150 mg / kg on day 4 ). the blood pressure and heart rate effects of a single oral administration of pbs , bipro whey protein isolate or the whey protein hydrolysate was evaluated over a period of 7 hours . resting values for cardiovascular variables measured every morning before any intervention during four consecutive days are shown in table 2 . as we can see , there was no significant difference between the basal mean arterial blood pressuire and heart rate values measured on days 1 , 2 , 3 and 4 . values are means ± sem ; n is the number of rats . ( groups represent those used to assess blood pressure and heart rate effects of single oral administration of vehicle ( pbs ), 601 , 603k , 605k or bipro whey protein isolate in conscious , unrestrained shr . map , mean arterial blood pressure ; hr , heart rate ; bpm , beats per minute . fig1 shows the changes in heart rate and mean arterial blood pressure after oral administration of 0 . 5 ml of 0 . 2 mm pbs ( n = 36 ) or hydrolysate 601 at doses of 30 ( n = 9 ), 75 ( n = 8 ) or 150 mg / kg ( n = 7 ) in conscious , unrestrained spontaneously hypertensive rats ( shr ). each point indicates the mean with standard errors shown by vertical lines . * p & lt ; 0 . 05 versus vehicle - treated group , anova followed by fisher &# 39 ; s test . hr , heart rate ; bpm , beats per minute ; map , mean arterial blood pressure . except for the 75 mg / kg dose , which elicited a significant ( at 4 , 6 and 7 h ) decrease in heart rate ( maximum of − 77 ± 14 bpm at 6 h ), we found no significant difference between the heart rate responses elicited by intra - gastric administration of pbs and hydrolysate 601 at the doses of 30 and 150 mg / kg . however , we observed a significant reduction in mean arterial blood pressure following intra - gastric administration of the different doses of hydrolysate 601 when compared to control administration of pbs . thus , at the dose of 30 mg / kg we observed a significant hypotensive effect (− 27 ± 6 mm hg ) 6 hours after administration of the hydrolysate . at the dose of 75 mg / kg of hydrolysate we observed a marked and long - lasting hypotensive effect ( significant at 1 - 7 h ) when compared with the effects of control administration of pbs . the maximum decrease in mean arterial blood pressure (− 39 ± 6 mm hg ) was achieved 6 h after the administration . a similar hypotensive effect was also observed following the intra - gastric administration of 150 mg / kg of the hydrolysate ( significant at 1 and 3 - 7 h ). the maximum decrease in mean arterial blood pressure (− 32 ± 7 mm hg ) was achieved 6 h after the administration . cardiovascular responses to bipro and hydrolysate 603k , 605k fig2 - 4 show the changes in heart rate and mean arterial blood pressure after oral administration of 0 . 5 ml of 0 . 2 mm pbs ( n = 36 ) or hydrolysate 603k ( fig2 ) or 605k ( fig3 ) or bipro whey protein isolate ( fig4 ) at doses of 30 , 75 , or 150 mg / kg . we found no significant difference between the heart rate or mean arterial blood pressure responses elicited by intra - gastric administration of pbs and hydrolysate 603k or 605k or bipro whey protein isolate at the different doses tested . single oral administration of hydrolysate 601 ( at the doses of 75 or 150 mg / kg ) in conscious unrestrained shr significantly reduced mean arterial blood pressure from 1 to 7 hours after administration . blood pressure returned to the initial level at 24 hours after administration . conversely , the hydrolysate 603k and 605k and the control bipro whey protein isolate ( at any of the doses tested ) did not change the mean arterial blood pressure of the shr rats in this study . a suitable regimen for treatment with the noted hydrolysate 601 will comprise oral administration of the above doses of 75 to 150 mg / kg at intervals of from 2 to 24 hours . more broadly , the dosages and intervals could be increased or decreased by from 50 to 500 percent , as might be indicated by treatment over time . the above description is intended to enable the person skilled in the art to practice the invention . it is not intended to detail all of the possible modifications and variations which will become apparent to the skilled worker upon reading the description . it is intended , however , that all such modifications and variations be included within the scope of the invention which is seen in the above description and otherwise defined by the following claims . the claims are meant to cover the indicated elements and steps in any arrangement or sequence which is effective to meet the objectives intended for the invention , unless the context specifically indicates the contrary .
enzymatic digests of whey protein isolates were prepared using animal , bacterial and fungal proteases , and evaluated for antihypertensive activities . the antihypertension activity was obtained with a hydrolysate of whey protein isolate prepared with a porcine trypsin . the recovered hydrolysate is used to treat hypertension in mammals such as humans and domestic pets such as dogs and cats .