24301
In contrast , zinc protoporphyrin ( ZnPP ) , a specific HO - 1 inhibitor , showed a partial suppressive effect of 5HHMF on LPS - induced NO production .
 zinc protoporphyrin, ZnPP, 5HHMF, NO
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 zinc protoporphyrin, ZnPP, 5HHMF, NO