Testosterone and cortisol concentration in spermatic, adrenal and systemic venous blood in adult male guinea pigs

Testosterone (T) and cortisol (F) concentrations were measured in spermatic vein, adrenal vein and systemic blood of adult male guinea pigs before and after 4 days of treatment with ACTH, methylprednisolone acetate (MPA), or HCG. In the untreated animal, T concentrations were 1.0 μg/100 ml in spermatic vein blood and 0.20 μg/100 ml in cardiac blood. Spermatic vein T concentration fell with ACTH, increased with HCG, and was unchanged by MPA treatment. The testosterone concentration in cardiac blood tended to be similar to adrenal venous blood levels and was always higher than in systemic blood obtained after organ blood collection. Normal F concentration was 488 μg/100 ml in adrenal vein and 50 μg/100 ml in cardiac blood. ACTH increased and MPA decreased all F levels. These results indicate that the testis is the main source of T secretion in the male guinea pig although the adrenal may secrete a biologically significant amount of gonadotropin suppressing steroid during pharmacological stimulation. There was no evidence of testicular F secretion. There was evidence that T production fell while F production was less labile during the period of organ blood collection.