ABSTRACT
To elucidate the Ca2+ release mechanisms in the rabbit coronary artery, arterial preparations were permeabilized with beta-escin and changes in tension were measured under varying experimental conditions. Additionally, we investigated properties and distribution of two kinds of Ca2+ release mechanisms, Ca2+-induced Ca2+ release (CICR) and IP3-induced Ca2+ release (IICR). The results obtained were summarized as follows; 1. When a rabbit coronary artery was incubated in a relaxing solution containing 30 microM beta-escin for 40 min. sensitivity to externally added Ca2+ was much higher in beta-escin permeabilized muscle than in intact preparations. The contractile effect of IP3 in beta-escin permeabilized muscle was also demonstrated; 2. Caffeine and IP3 contracted coronary arteries were permeabilized with beta-escin, but the amplitude of contraction was much larger in the presence of caffeine than of IP3. 3. Intracellular heparin completely inhibited the contractions induced by IP3, but not those by caffeine. On the other hand, procaine inhibited the responses to caffeine, but not those to IP3. Ryanodine inhibited both the caffeine- and IP3-induced contractions. 4. The amplitude of contractile responses was much larger to the maximal stimulation of CICR by applying caffeine than to the maximal stimulation of IICR by applying IP3. After the maximal CICR stimulation by caffeine, the activation of IICR by IP3 without the reloading of Ca2+ could no longer evoke contraction. On the other hand, after the maximal IICR activation, the activation of CICR could still evoke contraction although the amplitude of the contraction was smaller when compared with the case without the initial IICR stimulation. 5. Acetylcholine contracted coronary artery smooth muscles were permeabilized with beta-escin. However, in the absence of added guanosine triphosphate (GTP), the responses were very small. Acetylcholine-induced contraction was inhibited by heparin, but not by procaine. From the above results, it may be concluded that there are two kinds of mechanisms of Ca2+ release, CICR and IICR, in the rabbit coronary artery smooth muscle cell. Also, whereas the CICR mechanism distributes on the membrane of the whole smooth muscle Ca2+ store, the IICR mechanism distributes only on a part of it.
Subject(s)
Rabbits , Animals , Arteries/metabolism , Calcium/metabolism , Capillary Permeability/drug effects , Coronary Vessels/drug effects , Escin/pharmacology , In Vitro Techniques , Intracellular Membranes/metabolism , Tissue DistributionABSTRACT
O presente trabalho foi desenvolvido com a utilizaçäo de antiinflamatórios de origem vegetal: bromelina, escina e papaína, em doses terapêuticas. Os antiinflamatórios foram injetados intraperitonealmente em ratas prenhas, com a finalidade de verificarmos os possíveis efeitos sobre o desenvolvimento óssseo das colunas vertebrais. Os resultados obtidos segundo as condiçöes de nossa pesquisa, foram: 1. As três drogas antiinflamatórias de origem vegetal - bromelina, escina e papaína - causaram reduçäo do crescimento das colunas vertebrais de ratas. 2. O grupo onde só as mäes tomaram papaína durante a prenhez, foi o mais atingido no crescimento da coluna vertebral, e o grupo onde as mäes e os filhotes tomaram papaína, foi o menos atingido. 3. Quanto ao crescimento, o grupo composto por animais que tomaram escina durante a prenhez, apresentou um aumento de peso significativo em relaçäo ao grupo controle. 4. Quanto à malformaçäo da coluna vertebral, todos grupos apresentaram leves deformaçöes em relaçäo ao grupo controle, sendo que o grupo onde as mäes e os filhotes tomaram escina, foi o que apresentou maior deformaçäo na estrutura da coluna vertebral