Contractile effects of intracellularly administered angiotensin II are partially dependent on membrane receptors internalization in isolated rat aorta.

In the present study we used the isolated rat aorta as a model to characterize the modulation of contractile effects of extra- and intracellularly administered angiotensin II by dithiothreitol (DTT) and hyperosmotic sucrose. DTT inactivation of AT1 receptor as well as disruption of the clathrin-coated pits by hyperosmotic sucrose significantly inhibited the contraction induced by intracellularly administered AII. We suggest that these intracellular effects of angiotensin peptides are associated with AT1 receptor activation/internalization and may thus be part of the mechanism of angiotensin peptides direct contractile effects in the vascular smooth muscle.

Contractile effects of angiotensin peptides in rat aorta are differentially dependent on tyrosine kinase activity.

It has been suggested that tyrosine kinase activity participates in the regulation of signal transduction associated with angiotensin II (Ang II)-induced pharmaco-mechanical coupling in rat aortic smooth muscle. We further tested the effects of genistein, a tyrosine-kinase inhibitor, and its inactive analogue, daidzein, on angiotensin I (Ang I), angiotensin III (Ang III) and angiotensin IV (Ang IV) contractions, as compared with those on Ang II. Genistein partially inhibited Ang II- and Ang I-induced contractions.

[The effects of the intraventricular administration of captopril on water and ion metabolism in the rst].

The effects of the conversion enzyme on the hydroelectrolytic balance in adult rats, maintained in standard lab conditions have been followed. The administration protocol for the conversion inhibitor (captopril) produced a blocking of the transformation of angiotensin I in angiotensin II only at the level of the cerebral structures, during the whole period of the treatment (40 micrograms/kg x 3/24 hours). Following the intracerebroventricular (ICV) administration of captopril, the fluid ingestion decreased diuresis and urinary elimination of Na+ and Ca++ increased.

[Dipsogenic behavior].

Hydroelectrolytic homeostasis assumes balance between the intake and elimination of water and electrolyte, according to the necessities of the organism. The water intake is made mainly by fluid ingestion. The necessity to drink is a subjective sensation which is the expression of an objective situation, because it translates the homeostatic deviations.

Vasorelaxant properties of brefeldin A in rat aorta.

The effects of brefeldin A, a putative specific agent that disassembles the Golgi apparatus were assessed on the contractility of de-endothelised rat aorta. Brefeldin A inhibited, either as pre- or as post-treatment, the contractions elicited by K+ (75 mM) or phenylephrine (10 microM), being significantly more potent upon the latter. The thapsigargin (1 microM)-induced rat aorta contraction was less sensitive to brefeldin A inhibition.