Parathyroid glands of amphibians. II. Structural and biochemical changes in amphibian tissues elicited by parathyroid hormone under varying conditions of season and temperature

Abstract

The parathyroid glands have received relatively little attention with regard to their impact on the internal milieu in amphibians. Present information, however, clearly indicates that distribution of mineral in frog tissues and body fluids is under hormonal regulation; further modifications are imposed by season and temperature. Under conditions of cold acclimation or during winter normal amphibian bone shows minimal rates of carbohydrate utilization: simultaneously, phosphate is conserved by reduced excretion and increased incorporation in tissue. Exogenous parathyroid hormone, injected under these conditions when endogenous titers may be low due to glandular degeneration, reverses these effects, and phosphate is lost in a hyperphosphaturic urine. During summer or periods of warm acclimation, hormone promotes incorporation of phosphate in tissues, and increases rates of carbohydrate metabolism in bone; citric acid, which may act in solubilizing bone mineral, is elevated in the bone. Concurrently, pre-existing sulfated mucopolysaccharides of "old" bone may be degraded, while epiphyseal zones enlarge and may exhibit accelerated or abnormal elaboration of sulfated components of cartilage and/or osteoid matrix. © 1967 by the American Society of Zoologists.