Alterations in binding characteristics of peripheral benzodiazepine receptors in testes by vitamin A deficiency in guinea pigs

The correlation of vitamin A with the binding characteristics of peripheral benzodiazepine receptors (PBRs) in testes have been implicated on the basis of findings of involvement of vitamin A in testicular physiology and the abundance of PBRs in testicular tissue. Both vitamin A and PBRs are involved in the control of cell proliferation and differentiation but no data exists regarding the relationship between them. In the present study, we have examined the effects of vitamin A deficiency on the affinity and density of PBRs in testes of guinea pigs. Weanling guinea pigs were divided into three groups: control, pair-fed control and vitamin A deficient. They were fed a complete semipurified diet. The vitamin A deficient diet was similar to the control diet except vitamin A palmitate was omitted. Vitamin A deficiency status was achieved after 90 days of feeding. Binding of [³H]Ro 5-4864, a specific ligand for peripheral benzodiazepine receptors was determined in whole homogenate of testicular tissue. There was a 77% decrease in the receptor density (B_max) in vitamin A deficient group compared to control. The B_maxvalues for control, pair-fed control and vitamin A deficient groups were: 12.4 ± 0.4, 8.8 ± 0.2 and 3.0 ± 0.6 pmol/g, respectively. The equilibrium dissociation constant (K_D) values were also 86% decreased in the vitamin A deficient group compared to the other groups. The K_D values for control, pair-fed control and vitamin A deficient groups were: 3.4 ± 0.7, 2.8 ± 0.5 and 0.5 ± 0.01, respectively. The decrease in the binding characteristics of PBRs in testes due to vitamin A deficiency was accompanied with a corresponding decrease in the levels of testosterone in plasma. These results suggest a close functional relationship of vitamin A with PBRs in testes.