Effect of Neurohypophyseal Hormones on Excretion of Proteins by the Kidneys

Abstract

Vasopressin (VP) is one of the main factors affecting intraglomerular hemodynamics, filtration pressure and the state of mesangial cells and contributing to the progression of proteinuria. The aim of this work was to study the effect of neurohypophyseal hormones (VP and oxytocin) on urinary protein excretion. Experiments were performed on Wistar rats, healthy and with microalbuminuria caused by minimal damage to the glomerular filter. Microalbuminuria was modeled by administration of D-nitroarginine methyl ester (D-NAME, 50 mg/kg, intraperitoneally). VP (0.05 and 1.5 nmol/kg) and oxytocin (0.15 nmol/kg) were administered to rats intramuscularly, V2-antagonist (15 nmol/kg) and V1a-antagonist (20 nmol/kg) intraperitoneally. To reduce the level of endogenous VP, animals were given water to drink (10 ml/kg), urine was collected for 2 h, and the levels of total protein, albumin, β2-microglobulin, and immunoglobulin G (IgG) were analyzed. In healthy rats, VP at a dose of 0.05 nmol/kg and oxytocin did not affect albumin excretion, but VP at a dose of 1.5 nmol/kg provoked microalbuminuria. In a model of impaired properties of the glomerular filter caused by the D-NAME administration, VP at a dose of 0.05 nmol/kg and oxytocin led to the normalization of albumin excretion, and VP at a dose of 1.5 nmol/kg caused pronounced proteinuria, albumin excretion increased by 100 times, IgG – by 10 times. Blockade of V2 receptors aggravated protein loss caused by D-NAME and VP (1.5 nmol/kg), while blockade of V1a receptors prevented it. Thus, at high concentrations in the blood, VP enhances protein filtration in the kidney. This effect is mediated by V1a receptors and, depending on the barrier properties of the glomerular filter, leads to the development of microalbuminuria or severe proteinuria. Oxytocin and VP at a dose at which it predominantly activates V2 receptors have an antiproteinuric effect. The revealed effects of neurohypophyseal hormones on albumin excretion open up new promising therapeutic targets for the correction of glomerular dysfunctions.