Vitamin D, parathyroid, and thymus gland influences on seasonal variations in renal electrolyte excretion.

Effects of the thymus gland and vitamin D and other calcium-regulating hormones on electrolyte balance were investigated. In studies conducted over 3 successive years male hooded rats excreted more chloride (Cl) and less inorganic phosphate (P) in April-August (summer) than in November-March (winter) when subjected to sham operation (SHAM) or to the surgical procedures described herein and exposed to natural sunlight in temperature- and humidity-controlled rooms. Parathyroidectomy, combined with sham thymectomy (PX), thymectomy (PX-TMX), thyroidectomy-sham thymectomy (TPX), or thyroidectomy-thymectomy (TPX-TMX), significantly increased Cl excretion during both seasons. The same surgical procedures also reduced P excretion in the winter. However, PX and PX-TMX lowered the P values only slightly in summer, and the effects were reversed by thyroid ablation. Thymectomy (TMX), alone or in combination with PX or TPX, increased Cl excretion during the summer, but it did not affect the outputs of winter animals with intact thyroid or parathyroid glands. Vitamin D3 (400 IU) injected three times weekly for 3 weeks increased the Cl excretion of all surgical groups during the winter. In the summer, it increased the Cl excretion of SHAM only, and it diminished the Cl excretion of thyroidectomized rats. Significant increases in P excretion were found only in PX-winter and TMX-summer groups. A vitamin D-deficient diet during the summer resulted in a more than four-fold increase in P excretion in TMX and SHAM rats, and it significantly reduced Cl excretion.(ABSTRACT TRUNCATED AT 250 WORDS)