TRH-DEGRADING ENZYME ACTIVITY IN PERIPHERAL AND PITUITARY-PORTAL PLASMA OF THE RAT

Abstract

ABSTRACT The enzymatic degradation of TRH was measured in peripheral and pituitary-portal plasma. Enzyme activity in peripheral plasma was 3.20 pg/min/μg plasma protein; in pituitary-portal plasma the rate of degradation was only 0.83 pg/min/μg protein. After dialysis, which removed virtually all endogenous TRH and LHRH, enzyme activity in peripheral and portal plasma was 2.24 and 0.60 pg/min/μg respectively. These data suggest that portal plasma contains large concentrations of unidentified substances which are competitive inhibitors or substrates for the enzyme or that portal plasma contains less TRH-degrading enzyme.