caa a22 4500 477120601 CHVBK 20180405111635.0 cr unu---uuuuu 170330e19960301xx s 000 0 eng 10.1007/BF00408654 doi (NATIONALLICENCE)springer-10.1007/BF00408654 Inositol-1,4,5-trisphosphate mass content in isolated perfused rat heart during alpha-1-adrenoceptor stimulation [Elektronische Daten] [Sigrid Hanem, Mette Enger, Tor Skomedal, Jan-Bjørn Osnes] Inositol-1,4,5-trisphosphate (IP3) has been proposed to be a second messenger in response to alpha-1-adrenoceptor stimulation also in myocardial cells. We studied the effect of alpha-1-adrenoceptor stimulation (5 × 10−5 mol/l phenylephrine or 5 × 10−5 mol/l noradrenaline both in the presence of 10−6 mol/l timolol) on IP3 mass content in isolated perfused rat hearts. IP3 content was determined by a specific receptor-binding assay-kit (TRK 1000, Amersham) after validating the method. For comparison also the effect of muscarinic stimulation (10−4 mol/l carbachol in the presence of 10−6 mol/l timolol) on IP3 content was measured in corresponding preparations. A basal IP3 level of about 75 pmol/mg protein was found. There were no prominent effects of alpha-1-adrenoceptor stimulation on total IP3 content in isolated perfused rat hearts. Phenylephrine gave a statistically significant increase of about 40% at 1/4 min and a statistically significant decrease of about 25% at 4 min after start of exposure. Noradrenaline, however, gave no statistically significant change of IP3 at the time-points studied. Muscarinic stimulation caused a slight, statistically insignificant, increase of IP3 at 1/4 min. The results are compatible with an assumption that agonist stimulation evokes a localized increase of IP3 which may be masked by a relatively high total IP3 mass content. The IP3 peak after phenylephrine coincided with the early positive inotropic phase of the response reported earlier in perfused rat hearts for alpha-1-adrenoceptor stimulation by phenylephrine. Although this might be compatible with a role for IP3 in this early and transient phase, a mediator function of IP3 in the inotropic response is not established. Kluwer Academic Publishers, 1996 IP3 nationallicence alpha-1-adrenoceptors nationallicence rat heart nationallicence phenylephrine nationallicence noradrenaline nationallicence Hanem Sigrid Department of Pharmacology, University of Oslo, P.O. Box 1057 Blindern, N-0316, Oslo, Norway aut Enger Mette Department of Pharmacology, University of Oslo, P.O. Box 1057 Blindern, N-0316, Oslo, Norway aut Skomedal Tor Department of Pharmacology, University of Oslo, P.O. Box 1057 Blindern, N-0316, Oslo, Norway aut Osnes Jan-Bjørn Department of Pharmacology, University of Oslo, P.O. Box 1057 Blindern, N-0316, Oslo, Norway aut Molecular and Cellular Biochemistry Kluwer Academic Publishers; http://www.wkap.nl 163-164/1(1996-03-01), 167-172 0300-8177 163-164:1<167 1996 163-164 11010 https://doi.org/10.1007/BF00408654 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00408654 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Hanem Sigrid Department of Pharmacology, University of Oslo, P.O. Box 1057 Blindern, N-0316, Oslo, Norway aut NATIONALLICENCE 700 1- Enger Mette Department of Pharmacology, University of Oslo, P.O. Box 1057 Blindern, N-0316, Oslo, Norway aut NATIONALLICENCE 700 1- Skomedal Tor Department of Pharmacology, University of Oslo, P.O. Box 1057 Blindern, N-0316, Oslo, Norway aut NATIONALLICENCE 700 1- Osnes Jan-Bjørn Department of Pharmacology, University of Oslo, P.O. Box 1057 Blindern, N-0316, Oslo, Norway aut NATIONALLICENCE 773 0- Molecular and Cellular Biochemistry Kluwer Academic Publishers; http://www.wkap.nl 163-164/1(1996-03-01), 167-172 0300-8177 163-164:1<167 1996 163-164 11010 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer