[Role of V1- and V2-receptors in mechanism of physiological paradox--an increase of reabsorption of the solute free water and simultaneous rise of diuresis].
In experiments on non-anesthetized rats with administration into stomach of water (5 ml/100 g body mass) direct correlation has been found between an increase of diuresis and excretion of solute free water (r = 0.98, p < 0.01), while after injection to these animals of 5 x 10(-11) M arginine-vasotocin - between an increase of diuresis and simultaneous rise reabsorption of solute free water (r = 0.8, p < 0.01). The rise of diuresis after the vasotocin injection is due to inhibition of sodium re- absorption, with the solute excretion fraction increasing from 2.6 +/- 0.2 % to 11.9 +/- 1.2, p < 0.001. A similar physiological paradox - an increase of diuresis with the simultaneous increase of reabsorption of solute free water - has been revealed at night hours in children with tendency for nocturnal enuresis (r = 0.64, p < 0.01). Mechanism responsible for this phenomenon consists in a rise of diuresis due to a decrease of sodium ion reabsorption in the ascending Henle loop limb. A problem is discussed of the homeostatic significance of a decrease of sodium reabsorption combined with an increase of solute-free water reabsorption; it is suggested that this phenomenon is based on a redistribution of reabsorption inside the nephron - a decrease of ion and water reabsorption in the initial parts of the nephron distal segment and an increase of solute free water reabsorption with the antidiuretic hormone-stimulated high osmotic permeability of terminal parts of renal tubules. An intraperitoneal injection of V1-anatagonist (OPC-21268) decreased the natriuretic component of response to arginine-vasotocin, while injection of V2-antagonist (OPC-31260) eliminated the antidiuretic component.
Kanashkina
T A
TA
Kuznetsova
A A
AA
Shakhmatova
E I
EI
Natochin
Iu V
IuV
D000042:Absorption; D000293:Adolescent; D000818:Animals; D065092:Antidiuretic Hormone Receptor Antagonists; D002648:Child; D002675:Child, Preschool; D004231:Diuresis / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006801:Humans; D007677:Kidney Function Tests; D053206:Nocturnal Enuresis / Q000503:physiopathology*; D009994:Osmolar Concentration; D051381:Rats; D017208:Rats, Wistar; D017483:Receptors, Vasopressin / Q000819:agonists / Q000378:metabolism*; D014668:Vasotocin / Q000494:pharmacology; D014867:Water / Q000502:physiology; D014882:Water-Electrolyte Balance
D065092:Antidiuretic Hormone Receptor Antagonists; D017483:Receptors, Vasopressin; D014867:Water; D014668:Vasotocin