Abstract
Superfusion of the portal vein of rat and guinea-pig with Krebs' solution maintained at 25 degrees C greatly inhibits spontaneous contractions of the preparations and allows contractile responses to ATP and noradrenaline to be measured accurately. Under these conditions, continuous superfusion with ATP (10(-5) M), a concentration which had no effect on either basal tension or spontaneous activity, caused a significant shift to the left of the concentration-response curve to exogenous noradrenaline in both tissues. The mechanism of this potentiation induced by ATP may differ in the two tissues since in the rat portal vein potentiation appeared to be rapidly reversed by superfusing with ATP-free solution, whereas in the guinea-pig portal vein a further concentration-response curve to noradrenaline, in the absence of ATP, was still significantly shifted to the left compared with the control curve. However, potentiation in the rat portal vein may have had a longer duration than is suggested by the results since control concentration-response curves to noradrenaline in this tissue showed a progressive shift to the right which, although not significant, is likely to have affected the apparent time course of potentiation. It is concluded that ATP can potentiate contractions to exogenous noradrenaline in the portal vein of rat and guinea-pig via an, as yet, unidentified postjunctional mechanism.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
