Cytoskeleton, passive tension and the contraction of the rat aorta to phorbol 12,13-dibutyrate.
The influence of passive tension on contractions to phorbol 12,13-dibutyrate (1 microM PBDu) on the thoracic aorta of Wistar and SHR rats, aged 8-12 weeks, and the functional importance of both the actin and the tubulin components of the cytoskeleton, were studied. Contractile responses to PBDu (1 microM) were obtained in aorta rings, at two levels of passive tension: 3 and 0.5g. These responses were expressed as percentage of the maximal response to noradrenaline obtained in the beginning of the experiment at a tension of 2g. Responses to PBDu were significantly larger (P<0.05) at 3g than at 0.5g in both kinds of rats: 226.5+/-34.4%, n=6, versus 143.0+/-28.5%, n=6, respectively, for SHR; 153.0+/-12.9%, n=8, versus 109.0+/-7.3%, n=7, respectively, for Wistar rats. Responses to PBDu were markedly decreased by cytochalasin B (50 microM) (to 61.3+/-14.3%, n=6, at 3g, and 29.6+/-17.8%, n=5, at 0.5g in SHR; to 18.5+/-0.9%, n=6, at 3g, and 6.4+/-1.8%, n=5, at 0.5g in Wistar rats). Colchicine (100 microM) failed to produce a decrease in responses to PBDu in both strains of rats. It is concluded that responses to phorbol ester action depend on passive tension. This difference may depend on filament interaction. Contractions to PBDu in the rat aorta may be highly dependent on actin polymerization.
Nunes
José Pedro L
JP
Faculdade de Medicina da Universidade do Porto, Institute of Pharmacology and Therapeutics, U38-FCT, 4200 Porto, Portugal. jplnunes@med.up.pt
D000199:Actins / Q000037:antagonists & inhibitors; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D003078:Colchicine / Q000494:pharmacology; D003571:Cytochalasin B / Q000494:pharmacology; D003599:Cytoskeleton / Q000378:metabolism / Q000502:physiology*; D006973:Hypertension / Q000503:physiopathology*; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D051381:Rats; D011918:Rats, Inbred SHR; D017208:Rats, Wistar; D050257:Tubulin Modulators
D000199:Actins; D050257:Tubulin Modulators; D015240:Phorbol 12,13-Dibutyrate; D003571:Cytochalasin B; D011493:Protein Kinase C; D003078:Colchicine