Plasma steroid and corticosteroid levels in female pacu Piaractus mesopotamicus, Teleostei-Characidae

We report the plasma levels of estradiol-l7Beta (E2), testosterone (T), 17(alpha-2Obeta-dihydroxy-4-pregnen-3-one (l7-2OP), and cortisol (F) in female pacu during the reproductive cycle (N = 44) and in females induced to ovulate with an analogue of luteinizing hormone releasing hormone (LHRHa; 10 mug/kg) (N = 24). The plasma hormone levels were determined by validated radioimmunoassays. Females sampled during the reproductive cycle were grouped into 4 gonadal stages: resting, early maturation, advanced maturation and regression. The calculated gonadosomatic index varied from 0.5 ñ 0.1 per cent in resting stage to 8.1 ñ 0.6 per cent in advanced maturation stage. The E2 and T values were highest during the early maturation stage (E2 = 2172 ñ 7.1 pg/ml; T = 412 ñ 58 pg/ml) and the F values were highest during the advanced maturation stage (l32 ñ 5 ng/ml). Females induced to ovulate by LHRHa injection were sampled at 0, 6, and 12 h after injection of LHRHa. Two additional groups were sampled at ovulation and 24 h after ovulation. The E2 values were highest at 6 h (2917 + 65 pg/ml). The T and F values were highest at ovulation (T = 3498 + 77 pg/ml; F = 387 ñ 16 ng/ml) and 17-20P was detected only at vulation (2163 ñ 80 pg/ml).

Effect of aging on the glutaminase activity of neoplastic and immune tissues

1. The effect of age and Walker 256 tumor on maximal phosphate-dependent glutaminase activity of rat immune tissue was determined. Glutaminase is a key enzyme in the metabolism of glutamine, an important fuel for normal and neoplastic cells. 2. Maximal activity of phosphate-dependent glutaminase was measured in immune tissues and tumors of Walker 256 tumor-bearing young (28 days old), mature (3 months old) and aged (15 months old) Wistar rats. The following tissues were examined: thymus, spleen, mesenteric lymph nodes and tumor. 3. Tumor implantation for 14 days reduced glutaminase activity in the thymus and mesenteric lymph nodes. Tumor glutaminase activity was lowest in aged rats and highest in the mature group. 4. Comparison of glutaminase activity in immune and tumor tissues suggested the flux of glutamine between these tissues in the 3 groups. Glutaminase activity was 2.8-fold higher in immune tissues in aged rats (2.58 +/- 0.35 vs 0.93 +/- 0.16 mumol min-1 g tissue wet weight-1, mean +/- SEM, 5 rats), and 1.9- (4.14 +/- 0.47 vs 8.36 +/- 1.29 mumol min-1 g tissue wet weight-1, mean +/- SEM, 5 rats) and 2.5-fold increased (2.41 +/- 0.20 vs 5.92 +/- 0.22 mumol min-1 g tissue wet weight-1, mean +/- SEM, 5 rats) in tumor tissue in the mature and young groups, respectively. These results suggest the deviation of glutamine flux from defense cells to the neoplastic tissue in tumor-bearing young and mature rats and may partially explain the slow cancer growth in elderly patients