The Effect of Angiotensin on Rat Intestinal Fluid Transfer

Abstract

Fluid transfer by isolated everted sacs of rat jejunum, ileum and intact colon prepared from adrenalectomized-nephrectomized rats 48 h after operation was reduced when compared with that of sacs prepared from untreated controls (P < 0\m=.\001).Angiotensin at 10\ m=-\ 10 g/ml significantly (P < 0\m=.\01) stimulated fluid transfer by intestinal sacs prepared from the adrenalectomized-nephrectomized rats; all three regions of gut were equally sensitive.Fluid transfer was similarly reduced in stripped colon sacs prepared from adrenalectomized-nephrectomized rats. Angiotensin had a dose-dependent biphasic action on fluid transfer by stripped colon sacs: low concentrations (10\m=-\11 and 10\m=-\12g/ml) stimulated (P < 0\m=.\05), whilst high concentrations (10\ m=-\ 9 and 10\m=-\8 g/ml) inhibited fluid transfer (P < 0\m=.\01).Histological examination of the colon preparations showed that the stripping procedure removed the ganglia, indicating that both angiotensin effects were due to direct action on the colon mucosa.The significance of these results is discussed in relation to the role of angiotensin in the control of salt and fluid transport by the mammalian kidney and other epithelial tissues.

Angiotensin II directly stimulates sodium transport in rabbit proximal convoluted tubules.

“…Angiotensin's ability to enhance norepinephrine release from sympathetic nerve endings is well known (16). Indeed, the stimulation of jejunal volume reabsorption by low doses of All appears due solely to the release of norepinephrine (33), whereas the effects on colonic transport persist after denervation (2). In the kidney, the initial clearance studies by McGiff(34) (30,37).…”

“…In addition to its role in aldosterone synthesis, All alters the slope ofosmolar antidiuretic hormone release (1), produces a central dipsogenic response and salt appetite (1), and enhances salt and water transport by the small intestine (2, 3) and colon (2,4,5).…”

Interactions between angiotensin peptides and the sympathetic nervous system mediating intestinal sodium and water absorption in the rat.

“…Therefore, it is possible that angiotensin II may act in the central nervous system to increase sympathetic outflow and, hence, jejunal water transport. Angiotensin II has been shown repeatedly to stimulate intestinal sodium and water transport in vitro (6,27). The hormone also stimulates sodium and water transport in intestinal preparations stripped of neural plexi (6).…”

“…The octapeptide hormone angiotensin II is a physiologically important sodium-retaining hormone, contributing to the maintenance of extracellular fluid volume by stimulating thirst (1), aldosterone production (2), vasopressin release (3), and transport of sodium and water across epithelial tissues (1)(2)(3)(4)(5)(6)(7). The effects of angiotensin II on transporting epithelia are concentration dependent.…”

“…The effects of angiotensin II on transporting epithelia are concentration dependent. In the isolated and in situ kidney (4,5) or the isolated intestine or jejunum in vivo (6,7), low physiological concentrations of angiotensin II stimulate net mucosal to serosal transfer of sodium and water, whereas high concentrations of the hormone inhibit transport and/or stimulate secretion. Changes in intestinal blood flow are not responsible for the effects of the hormone on transport in vivo (7).…”