Subtypes of neurohypophyseal nonapeptide receptors and their functions in rat kidneys

Abstract

The nonapeptides of neurohypophysis, vasotocin and mesotocin, detected in most vertebrates, are replaced by vasopressin and oxytocin in mammals. Using bioinformatics methods, we determined the spectrum of receptor subtypes for these hormones in mammals and their physiological effects in the kidneys of rats. A search for sequences similar to the vertebrate vasotocin receptor by proteomes and transcriptomas of nine mammalian species and the rat genome revealed three subtypes of vasopressin receptors (V1a, V1b, and V2) and one type of oxytocin receptors. In the kidneys of non-anesthetized rats, which received a water load of 2 ml per 100 g of body weight, three effects of vasopressin were revealed: 1) increased reabsorption of water and sodium, 2) increased excretion of potassium ions, and 3) increased excretion of sodium ions. It has been suggested that each of the effects on the kidney is associated with selective stimulation of the vasopressin receptor subtypes V2, V1b, and V1a depending on the concentration of nonapeptide. In experiments on non-anaesthetized rats with a water load, the injection of oxytocin reduces the reabsorption of solute-free water in the kidneys and increases the excretion of sodium ions. The possible physiological mechanisms behind the realization of both effects with the participation of a single type of oxytocin receptors are being analyzed. Thus, the spectrum of activated receptor subtypes varies depending on the current concentration of neurohypophyseal hormones, as a result of which the predominant effect on renal function changes, which ensures precise regulation of water-salt homeostasis.

Characterization of a functional V1B vasopressin receptor in the male rat kidney: evidence for cross talk between V1B and V2 receptor signaling pathways

“…The presence of the gene encoding V 1B R within the renal medulla has been previously mentioned (14,32,33). For the first time, we identified and characterized V 1B R in the IMCD using original ligands such as selective V 1B fluorescent or radioactive agonists and antagonist.…”

The Mechanism of the Solute-Free Water Reabsorption Increase in the Rat Kidney by Oxytocin Saluresis

“…These effects are due to the stimulation of different subtypes of V receptors [ 2 , 4 , 5 ]. In contrast to vasopressin, which has three subtypes of these receptors, only one type of oxytocin receptor gene was found in the rat genome [ 6 ]. Two assumptions have been made about the molecular mechanism of action of oxytocin on the reabsorption of water and sodium in the kidney.…”