[Characteristics of the K(+)-ion transport in the rat intestine following the use of natural zeolites as food additives]. / Osobennosti transporta ionov K(+) v kishechnike krys pri ispol'zovanii prirodnykh tseolitov v kachestve pishchevoi dobavki.

Effects of zeolites as a food supplement have been studied on Wistar rats both in vivo perfusion experiments in the jejunum and distal colon and Rb fluxes through intestinal wall in the Ussing chamber. It has been found that zeolites decrease the K+ absorption and stimulate K+ secretion in the gut. This effect was due to inhibition of the apical N(+)-K(+)-ATPase and ouabain-sensitive Na(+)-independent K(+)-ATPase as well as the activation of the basolateral N(+)-K(+)-ATPase.

[Effect of natural zeolites on renal functions and water-salt metabolism in rats]. / Vliianie prirodnykh tseolitov na funktsii pochek i vodno-solevoi obmen u krys.

In vivo experiments on adult Wistar rats, it has been found that intake of natural zeolites resulted in temporary decrease of renal water, sodium and potassium excretion. At the same time, reabsorption of water and electrolytes increased. This effect was due to the stimulation of Na+, K(+)-ATPase activity in thick ascending limb of Henle loop and hormonal changes: increase of insulin, thyroxin and aldosterone concentration in plasma. The water and ion content in most of the tissues under study was higher in the experimental group than in control. It has been suggested that renal response in rats with zeolites intake was compensatory lower as a result of gastrointestinal losses of ions and ion accumulation in tissues.

Regulation of K+ transport in the rat distal colon via angiotensin II subtype receptors and K+ -pathways.

The role of angiotensin subtype-1 (AT1) and -2 (AT2) receptors in mediating the effects of angiotensin II (ANG II) on several K+ transporters was studied in rat distal colon using an Ussing chamber. Angiotensin II induced K+ secretion at two different doses. Secretion occurred at 10-(8) and 10-(4) M, as a result of an increase in serosal-to-mucosal flux (Js-m). The ANG II-induced stimulation of Js-m at a low dose (10-(8) M) was abolished by PD123319 while losartan did not alter the low-dose ANG II-dependent increase in Js-m. In contrast, the increase in Js-m induced by a high-dose of ANG II (10-(4) M) was blocked by losartan, whereas PD123319 partially reduced the stimulatory effect. In the presence of both blockers, high-dose ANG II induced an inhibition of basal Js-m. Low-dose ANG II activated the barium-sensitive K+ channels, whereas the Na+, K+, 2Cl- cotransporter and the Na+, K+ -ATPase pump were unchanged. At the high dose, ANG II activated the barium-sensitive K+ channels and the Na+, K+, 2Cl- cotransporter and inhibited the Na+, K+ -ATPase pump. These data indicate that ANG II stimulates serosal-to-mucosal K+ flux in the rat distal colon at high and low doses via different receptors and K+ transporters.

[Age characteristics of K(+) transport in the rat distal colon]. / Vozrastnye osobennosti transporta K(+) v distal'nom otdele tolstogo kishechnika krys.

In vitro and in vivo experiments with perfusion in 20- and 60-day old rats revealed that K+ absorption in the gut as well as 86Rb uptake in the distal colon was significantly higher in younger rats due probable, to the higher activity of the apex-located K+-dependent ATPase and lower activity of the basolateral K+-carriers. The luminal blockade of K+ absorbing pumps with ouabain or omeprazole resulted in a decrease of the K+ absorption and K2 accumulation in skeletal muscles. The higher K+-absorbing/K_ secreting mechanisms ratio in younger rats contributes to the positive potassium balance.