Rat Testicular Phospholipase A₂ Activity: pH Optima, Its Cellular and Subcellular Distribution in the Gonad, and Some Factors That May Modulate Its Activity

Abstract

A sensitive radiometric assay was developed for detecting phospholipase A 1 and A 2 (PLA 1 and A 2 ) activity. Four to five times more PLA 2 activity was observed in rat testes than PLA 1 activity. Two PLA 2 were observed in the testis, one with an acid (3.5) and one with an alkaline (7.5–8.0) pH optimum. The acid pH optimal PLA 2 was located in the interstitial and lysosomal fractions. The alkaline pH optimal PLA 2 was localized in the germinal elements of the seminiferous tubules and in the lysosomalenriched and membrane‐enriched fractions. Triton X‐100 inhibited PLA 2 at 10 −2 M and inhibited PLA 1 at 10 −3 . At 10 −2 PA, triton X‐100 activated PLA 1 . EGTA inhibited PLA 2 activity, whereas Ca ++ at 10 −2 to 10 −3 M restored this activity. Corticosterone had no effect on PLA 2 activity, but progesterone, dihydrotestosterone, and testosterone all stimulated the enzyme at lower concentrations (10 −9 ‐10 −7 M), with testosterone giving maximUm stimulation at a lower dosage (ie, 10 −9 M compared to 10 −7 M for dihydrotestosterone). Both androgens inhibited PLA 2 activity at higher concentrations.