Quantification of cysteine sulfinic acid decarboxylase in male and female rats: effect of adrenalectomy and methionine.

Hepatic cysteine sulfinic acid decarboxylase (EC 4.1.1.29) activity has been reported to decrease in response to both L-methionine (Met) feeding and adrenalectomy in rats. A series of experiments was conducted to (a) determine if CSAD depression was evident in female rats fed a methionine-supplemented diet; and (b) determine if adrenal hormones mediated the response of CSAD to dietary methionine. Cysteine sulfinic acid decarboxylase (CSAD) activity was measured in livers of male and female rats fed a methionine-supplemented diet. In female rat liver, CSAD activity was only 25% of the activity measured in livers of male rats. Hepatic enzyme activity in male rats fed a casein-based basal diet containing 0.6% L-methionine was 2.5-fold higher than activity in male rats fed a methionine-supplemented diet containing 1.35% L-methionine (+Met). Similarly, enzyme activity in livers of female rats fed the basal diet was 1.7-fold higher than in female rats fed a methionine-supplemented diet. CSAD activity in adrenalectomized (ADX) male rats fed the basal diet was depressed (990 +/- 120 nmol/min.g liver) compared to activity in intact controls (2347 +/- 89) and sham controls (2040 +/- 143) fed the basal diet. CSAD activity was further depressed in ADX, intact controls, and sham controls fed +Met. Immunochemical detection and quantification of CSAD protein in rat liver demonstrated that changes in CSAD protein were consistent with the observed decreased enzyme activity in female rats, ADX rats, and rats fed +Met. S-Adenosylmethionine and S-adenosylhomocysteine concentrations tended to increase in livers of rats fed +Met. ADX rats fed +Met had the greatest increase in S-adenosylmethionine and S-adenosylhomocysteine concentrations. The depression in hepatic CSAD observed after feeding +Met to rats does not appear to involve adrenal function.