1. Regulation of the avian kidney by arginine vasotocin.
- Author
-
Goldstein DL
- Subjects
- Amino Acid Sequence, Animals, Aquaporins metabolism, Birds metabolism, Cyclic AMP metabolism, Glomerular Filtration Rate drug effects, Kidney anatomy & histology, Kidney Tubules drug effects, Molecular Sequence Data, Receptors, Vasopressin metabolism, Renal Artery drug effects, Second Messenger Systems physiology, Urination drug effects, Vasotocin chemistry, Vasotocin pharmacology, Water-Electrolyte Balance drug effects, Birds physiology, Kidney physiology, Vasotocin physiology
- Abstract
Nonapeptides secreted by the neurohypophysis have important roles in vertebrate cardio-fluid homeostasis. In birds, those peptides include mesotocin (the representative of the neutral, or oxytocin-like, nonapeptide family) and vasotocin (the representative of the basic, or vasopressin-like, hormones). The function of mesotocin is not well defined, but it does appear to have osmoregulatory functions. Vasotocin is considered the primary avian antidiuretic hormone. Receptors for AVT in avian kidney-either on renal vasculature or on the tubules-have yet to be localized or identified. However, AVT quite certainly effects antidiuresis via both vascular and tubular mechanisms. The former entail a reduction in the rate of glomerular filtration, apparently via constriction of afferent arterioles. Evidence for the latter (direct tubular action of AVT) has accumulated in recent years and includes enhanced fractional tubular water reabsorption, activation of second messenger (cAMP) in thick ascending limbs and collecting ducts, and modest AVT-stimulated water permeability in collecting ducts associated with expression of aquaporins. The relative importance of the renal vascular vs. tubular actions in birds likely depend on the dose of the hormone, the physiological condition of the animal, and the species of bird.
- Published
- 2006
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