title: The mechanism of the acid activation of rabbit uterine renin.
abstract: Besides active renin an inactive form of renin could be demonstrated in uterine tissue. On gel filtration it was eluted as a molecule of slightly higher molecular weight than active renin, and it could be irreversibly activated by acidification at 37 degrees C. The activation had a pH optimum between pH 3.8 and pH 5.3. Acid activated uterine renin was found identical to active uterine renin by 1) the formation of angiotensin I with time after addition of rat substrate, 2) the pressor response in the rat, 3) neutralization by antirenin and 4) similar Michaelian constants. Repeated freezing and thawing, acidification at 4 degrees C and dialysis against 4 mol/l NaCl did not give any activation. A lower rate of activation of diluted samples and activation by trypsin at pH 7.4 suggest that proteolytic enzymes are involved in the activation.
mesh_terms: D000804:Angiotensin II / Q000096:biosynthesis; D000818:Animals; D001681:Biological Assay; D002850:Chromatography, Gel; D004492:Edetic Acid / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D005615:Freezing; D006863:Hydrogen-Ion Concentration; D007461:Iodoacetates / Q000494:pharmacology; D008970:Molecular Weight; D010664:Phenylmethylsulfonyl Fluoride / Q000494:pharmacology; D011247:Pregnancy; D011817:Rabbits; D011863:Radioimmunoassay; D012083:Renin / Q000378:metabolism*; D013696:Temperature; D014357:Trypsin / Q000494:pharmacology; D014461:Ultracentrifugation; D014599:Uterus / Q000201:enzymology*
chemical_list: D007461:Iodoacetates; D000804:Angiotensin II; D010664:Phenylmethylsulfonyl Fluoride; D004492:Edetic Acid; D014357:Trypsin; D012083:Renin