Sexual development of hypernatriophilic male rats up to puberty

The sexual development of normonatriophilic (Normo) and hypernatriophilic (Hyper) male Wistar rats was compared from 30 to 60 days of age (N = 8-10 per group) with emphasis on the onset of puberty. Hyper rats (more than 5 ml of saline a day in a situation of free access to tap water and 1.5% NaCl) had a 20-39% body weight reduction and a 22-29% testicular growth rate decrease compared to Normo rats. Plasma testosterone (ng/ml) of Normo rats increased from 0.29 +/- 0.02 at 30 days to 1.42 +/- 0.18 at 50 days, decreasing to 0.87 +/- 0.15 at 60 days of age, with no significant difference compared to Hyper animals. Plasma concentration (ng/ml) of luteinizing hormone (LH) was significantly lower in Hyper (0.21 +/- 0.03) than in Normo (0.43 +/- 0.06) rats at 40 days. At 30 days, plasma follicle stimulating hormone (FSH) levels (ng/ml) were significantly higher in Hyper (18.9 +/- 1.3) than in Normo (15.6 +/- 0.5) rats. It is possible that increased levels of FSH compensated for a reduced amount of LH, thus allowing similar testosterone production by Hyper and Normo rats. At 30 days, testis maturation was higher in Hyper rats, as indicated by a 22% increase in tubular cross-sections with young spermatids. At 50 days, spermatogenesis progressed to the production of mature spermatids (onset of puberty) and Hyper rats exhibited an 18.7% lower rate of testis maturation. Testis maturation was similar in Hyper and Normo rats at 60 days.