The effect of a deficiency of ascorbic acid (AsA) on in-vivo testosterone production in mature male rats was investigated using a mutant strain of rats (ODS rats) unable to synthesize AsA. Male 60-day-old rats were fed AsA-deficient lab chow for 28 days with [ODS(+)] or without [ODS(-)] AsA supply. The AsA levels in the liver of ODS(-) rats were undetectable and those in the testes decreased to about 25% of those in ODS(+) rats by day 28. Plasma LH levels in ODS(-) rats decreased to about 30% of those in ODS(+) rats by day 28. However, there were no significant differences in the plasma levels of testosterone, or in the relative weights of seminal vesicles and ventral prostates between ODS(+) and ODS(-) rats. Plasma levels of testosterone in ODS(-) rats after a single injection of 200 IU hCG changed similarly to that in ODS(+) rats. The metabolic clearance rate of testosterone was also the same at 60 min after an intravenous injection of [3H]testosterone in both groups. These results indicate that AsA-deficiency in adult rats causes no significant change in basal plasma levels of testosterone or in the response to hCG, despite decreased plasma LH levels.

Adult male rats were repeatedly treated with ethane dimethanesulfonate (EDS), an agent known to destroy Leydig cells selectively. Following a second injection, changes in serum testosterone levels and histological and morphometric changes of Leydig cells showed the time course to be similar to those after the first treatment. The number and volume of Leydig cells markedly decreased at day 2, began to increase from day 7, and recovered to the values of the control rats at day 30, concomitant with the changes of serum testosterone levels. Cells in the interstitial tissue labeled with bromodeoxyuridine markedly increased in number at day 2, gradually decreased thereafter, and returned to the values of the controls at day 14. During this period, cells undergoing mitosis were seen, their type unable to be determined, but were presumed to be regenerating Leydig cells. Even 30 days following four treatments with intervals of 30 days each, serum testosterone levels were the same as those in the controls. Also the numerical and volume densities of Leydig cells and the volume of an average Leydig cell were the same as those of the controls. Mitosis was observed in mature Leydig cells at this period, if any. It appears that new Leydig cells began to proliferate by division earlier than 14 days after EDS, allowing that there were several stages of proliferation, and that the source of reappearing Leydig cells may not be a limited number of precursor cells, implying the presence of stem cells for Leydig cells.

Since our previous study revealed low basal testosterone (T) levels and a failure in response to an acute stimulation with human chorionic gonadotropin (HCG) despite of a good response to chronic stimulation in scorbutic mutant rats, time course of the response to HCG was studied and plasma LH level was measured in young adult rats deficient in ascorbic acid for 3 weeks. A single subcutaneous injection of HCG (200 IU) elevated T levels only slightly in plasma and not in testicular tissues of scorbutic rats 1 h after the injection when the levels in ascorbutic rats reached a maximum, while it yielded the same response pattern as in ascorbutic rats after 3 h. A pretreatment with HCG to scorbutic rats for 1 or 4 days resulted in the same response of plasma T as in ascorbutic rats. Plasma LH levels in unstimulated scorbutic rats were about 40% of those in ascorbutic rats. These findings indicate that a prolonged deficiency of ascorbic acid decreases plasma LH, and may reduce the sensitivity of testes to LH.