Enhanced daily sperm production in the remaining testis of aged rats following hemicastration.

Abstract

To investigate the effects of age and hemicastration on daily sperm production (DSP), testes from adult (6 to 10 months) and aged (22 to 24 months) Sprague‐Dawley rats were evaluated before and four months after hemicastration. Testes were weighted, decapsulated, homogenized in a Waring Blender, and evaluated for the number of maturation‐phase spermatids in the homogenates. DSP per testis was calculated by dividing the number of spermatids in the homogenates by the estimated life span of the spermatids (6.3 days). The same testicular traits, along with plasma LH and FSH levels, were determined in a second group of aged rats. Considering both testes in the first experiment, neither DSP per testis nor DSP per g parenchyma were significantly affected by age. However, the age testis interaction was significant (P < 0.01) in both parameters. DSP per g of the testis removed at hemicastration was slightly lower (P < 0.05) in the aged group, and DSP per g in the aged rat was enhanced (P < 0.05) in the hemicastrates. Unlike the adults, aged rats had enhanced (P < 0.01) DSP per testis in the remaining testis posthemicastration. In the second experiment, testicular weight, DSP per g, and DSP per testis were enhanced (P < 0.01) after hemicastration. Plasma FSH levels were significantly (P < 0.01) elevated within one week after hemicastration and remained elevated four months later. Plasma LH levels were not elevated within one week after hemicastration but were significantly (P < 0.01) elevated four months following hemicastration.We concluded that: 1. measured by DSP, no decline in spermatogenesis was found between 6 to 10 and 22 to 24 months of age; 2. aged rats were capable of hemicastration‐induced testicular enlargement and enhancement of DSP, 3. rats in the adult group were not capable of these hemicastration‐induced changes, 4. posthemicastration testicular enlargement was accompanied by an increased number of germ cells; 5. immediate and continued elevation of plasma FSH suggests its involvement in hemicastration‐induced testicular enlargement of aged rats.