Facilitory role of thyroid hormone in vitamin A uptake in the rat testes.
The inter-relationship of hormones and retinol (vit. A) metabolism is under investigation in our laboratory. The investigation is designed to study the role of thyroid hormone (tetraiodothyronine, T4) in the uptake of vit. A in various rat tissues. Adult male thyroidectomized (Tx) rats, partially vit. A deficient, were administered intragastrically tritium-labeled vit. A. Twenty-four hours later, the level of radioactivity was measured in the blood plasma, liver, kidneys, testes and urine collected for 24 hrs. The data showed that in Tx rats, there was a significant decrease (P less than .01) in the level of radioactivity in the kidneys, testes and urine; in blood plasma and the liver, there was a significant increase (P less than .01). In Tx rats, treatment with T4 restored 50-70% of the radioactivity lost in the kidneys, testes and urine. The endogenous vit. A level in Tx rats treated without and with T4 followed essentially the same pattern. The capacity of cellular retinol binding protein (CRBP) to bind exogenously added vit. A was examined. The data showed a decrease in the binding capacity of CRBP in Tx rats. We conclude that T4 facilitates the uptake of vit. A in the target tissues by regulating CRBP synthesis or degradation.
Department of Obstetrics and Gynecology, Howard University College of Medicine, Washington, D.C. 20059.
S
S
Rajguru
M
M
Nahavandi
B
B
Ahluwalia
D000818:Animals; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012177:Retinol-Binding Proteins / Q000378:metabolism; D054840:Retinol-Binding Proteins, Cellular; D054839:Retinol-Binding Proteins, Plasma; D013737:Testis / Q000378:metabolism*; D013965:Thyroidectomy; D013974:Thyroxine / Q000097:blood / Q000502:physiology*; D014284:Triiodothyronine / Q000097:blood / Q000502:physiology; D014801:Vitamin A / Q000493:pharmacokinetics*
D012177:Retinol-Binding Proteins; D054840:Retinol-Binding Proteins, Cellular; D054839:Retinol-Binding Proteins, Plasma; D014284:Triiodothyronine; D014801:Vitamin A; D013974:Thyroxine