dinoprost and 12-deoxyphorbol-13-isobutyrate

Role of h1 calponin on Ca2+-sensitivity of smooth muscle contraction was investigated using h1 calponin gene-deficient mice (CP -/-) and wild type mice (CP +/+). PGF2. induced a comparable force in intact aorta of CP +/+ and CP -/-. DPB showed similar effects to PGF2alpha. In membrane-permeabilized ileal smooth muscle, PDBu enhanced Ca2+-sensitivity of contraction comparably in CP +/+ and CP -/-. GTPgamma-S showed similar effects. Our results suggest that h1 calponin does not regulate Ca2+-sensitivity in the contractile mechanism of smooth muscle.

Topics: Animals; Aorta; Calcium Chloride; Calcium-Binding Proteins; Calponins; Dinoprost; Guanosine 5'-O-(3-Thiotriphosphate); Ileum; Mice; Microfilament Proteins; Muscle Contraction; Muscle, Smooth; Oxytocics; Phorbol Esters

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.

Topics: Animals; Calcium; Dinoprost; Egtazic Acid; In Vitro Techniques; Male; Muscle, Smooth, Vascular; Permeability; Phorbol Esters; Protein Kinase C; Rats; Rats, Wistar; Tetradecanoylphorbol Acetate

Norepinephrine (NE), prostaglandin F2 alpha (PG), 12-deoxyphorbol 13-isobutyrate (DPB) and high K+ induced sustained increase in cytosolic Ca2+ [( Ca2+]i) and muscle tension in rat aorta. Verapamil, at the concentration which abolished the high K(+)-induced changes, also abolished the increase in [Ca2+]i due to NE, PG and DPB although contractions were only partially inhibited. Excess EGTA further decreased [Ca2+]i although a part of the contraction was not inhibited. These results indicate that the sustained contractions induced by NE, PG and DPB are due to increase in [Ca2+]i, increase in Ca2+ sensitivity of contractile elements, and a Ca2(+)-independent mechanism.

Topics: Animals; Aorta, Thoracic; Calcium; Cytosol; Dinoprost; Egtazic Acid; In Vitro Techniques; Male; Muscle Contraction; Muscle, Smooth, Vascular; Norepinephrine; Phorbol Esters; Potassium; Rats; Rats, Inbred Strains; Verapamil