Hori M, Sato K, Miyamoto S, Ozaki H, Karaki H. Different pathways of calcium sensitization activated by receptor agonists and phorbol esters in vascular smooth muscle.
Br J Pharmacol 1993;
110:1527-31. [PMID:
8306097 PMCID:
PMC2175865 DOI:
10.1111/j.1476-5381.1993.tb13996.x]
[Citation(s) in RCA: 56] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
1. It has been shown that receptor agonists and activators of protein kinase C, phorbol esters, increase Ca2+ sensitivity of contractile elements in vascular smooth muscle. To discover if protein kinase C is involved in the agonist-mediated Ca2+ sensitization, we examined the effects of receptor agonists in the rat isolated aorta in which protein kinase C activity had been diminished by pretreatment with phorbol 12-myristate 13-acetate for 24 h. 2. In the aorta with protein kinase C activity, a high concentration (1 microM) of 12-deoxyphorbol 13-isobutyrate induced contraction and a low concentration (100 nM) potentiated high K(+)-induced contraction. In addition, prostaglandin F2 alpha induced greater contractions than high K+ at a given cytosolic Ca2+ level. The maximally effective concentrations of noradrenaline and endothelin-1 also induced greater contraction than high K+. In the aorta without protein kinase C activity, the contraction induced by 12-deoxyphorbol 13-isobutyrate and its potentiation of the high K(+)-induced contraction were abolished. However, prostaglandin F2 alpha, noradrenaline and endothelin-1 still induced a greater contraction than high K+. 3. In the aorta without protein kinase C activity, noradrenaline, endothelin-1 and prostaglandin F 2 alpha, but not 12-deoxyphorbol 13-isobutyrate, induced contractions in the presence of the Ca2+ channel blocker, verapamil, or in the absence of external Ca2+, by increasing Ca2+ sensitivity. 4. In the permeabilized preparations, inhibition of protein kinase C activity abolished the effect of potentiation of the Ca(2+)-induced contraction by 12-deoxyphorbol 13-isobutyrate although the potentiation of the contraction by prostaglandin F2 alpha did not change. 5. These results suggest that there are two pathways for Ca2+ sensitization in rat aorta; a protein kinase C-dependent pathway which is activated by phorbol esters, and a protein kinase C-independent pathway which is activated by receptor agonists.
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