The food intake of six rams was restricted for 3 months, resulting in a reduction of body fat to less than 12% of live weight, compared with 25 to 49% in well-fed controls. At the end of this period of undernutrition, blood flow and the uptake of oxygen and glucose in unit weight of testis, when estimated during anaesthesia, were lower than in the controls, and testis weight was reduced. The fraction of oxygen uptake that could be accounted for by the oxidation of glucose was unchanged, although the respiratory quotient was slightly higher in the underfed rams. Oxygen uptake by homogenates and mitochondria from the testes of underfed rams was lower under most conditions of incubation applied.
Testosterone output (mg/ram/day±s.e.m.) was 0·4±0·2 in the underfed rams and 3·5±0·7 in well-fed controls; in six other well-fed rams, sampled while conscious, testosterone output was 2·8±0·3. Spermatogenic activity, as indicated by the diameter of the seminiferous tubules and the sperm content of the epididymis, and accessory gland activity, as indicated by the weight and fructose content of the seminal vesicles, were lower in the underfed rams. All these indices appeared to be related to testosterone output when the latter was less than 2·5 mg/ram/day, but tended to attain maximal values at higher rates of hormone production
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