Insulin stimulates volume absorption in the rabbit proximal convoluted tubule.

Abstract

The present in vitro microperfusion study examined whether insulin affects volume absorption (J.) in the proximal convoluted tubule (PCT). PCT were perfused with an ultrafiltrate-like solution and were bathed in a serum-like albumin solution. Addition of a physiologic concentration of 10-10 M insulin to the bathing solution resulted in a stimulation of J. and a more negative transepithelial potential difference (PD). There was a progressive stimulation of the lumen negative PD and J, with higher insulin concentrations. Maximal stimulation occurred at 10-" M bath insulin. The insulin-induced stimulation of volume reabsorption was also observed when glucose and amino acids were removed from the luminal perfusate. Direct examination of the effect of insulin on glucose, chloride, and bicarbonate absorption demonstrated that the transport of all these solutes was stimulated by insulin. Addition of insulin to the luminal perfusate had no affect on J,. These data show that insulin has a direct effect to stimulate J. in the proximal tubule.

Glycogen synthase kinase 3 inhibition improves insulin-stimulated glucose metabolism but not hypertension in high-fat-fed C57BL/6J mice

“…Epidemiological studies indicate that insulin resistance and arterial hypertension are interrelated [35,36]. It has been suggested that the prohypertensive action of insulin could be due to increased sodium reabsorption by acting on distinct segments of the renal tubule [37][38][39]. A feedback mechanism limits insulininduced sodium retention when extracellular fluid volume is expanded [40], which is impaired in rats with hypertension associated with insulin resistance [41].…”

Metabolic syndrome and renal sodium handling in three ethnic groups living in England

“…In humans, insulin has an acute antinatriuretic effect [20], even in obese persons resistant to other metabolic effects of the hormone [21]. Although insulin is thought primarily to affect distal tubular sodium re-absorption [21,22,23,24], there is evidence of a direct insulin action on proximal tubular sodium re-absorption [25,26]; moreover, insulin receptors have been found in the proximal tubule of different species [27,28,29]. Finally, insulin increases the expression and the activity of sodium-hydrogen exchange isoform 3, which mediates more than 60% of the sodium re-absorption at the proximal tubule [30].…”

“…Hyperglycaemia in vitro favours antinatriuresis due to enhanced glucose-sodium co-transport in the convoluted proximal tubule [25]. In vivo proximal sodium re-absorption is stimulated by hyperglycaemia in rats [36], and is higher in patients with diabetes [37].…”

The Interrelationships between Fasting Serum Insulin Level, Obesity and Blood Pressure in Women: Results from a Cross-Sectional Population Study of Women in Gothenburg, Sweden.

“…There are several possible mechanisms by which insulin could increase blood pressure. Insulin increases sodium and water reabsorption in the proximal tubules of the kidney (22). Even with increased peripheral insulin resistance, as in hypertension (23) and obesity (24), the effect of insulin in the kidney seems to be preserved.…”