nonDonnan distribution of CI in smooth muscle is not caused by sequestration in organelles, and that considerations of osmotic equilibrium and electroneutrality suggest the existence of unidentified nondiffusible anions
ثبت نشده
چکیده
Electron probe analysis of dry cryosections was used to determine the composition of the cytoplasm and organelles of rabbit portal-anterior mesenteric vein (PAMV) smooth muscle. All analytical values given are in mmol/kg wt --+ SEM. Cytoplasmic concentrations in normal, resting muscles were: K, 611 --1.7; Na, 167 _+ 2.7; C1, 278 -+ 1.0; Mg, 36 --1.1; Ca, 1.9 -+ 0.5; and P, 247 --1.1. Hence, the sum of intracellular Na + K exceeded cytoplasmic C1 by 500 mmol/kg dry wt, while the calculated total, nondiffusible solute was 5 0 mmol/kg. Cytoplasmic K and C1 were increased in smooth muscles incubated in solutions containing an excess (80 mM) of KC1. Nuclear and cytoplasmic Na and Ca concentrations were not significantly different. The mitochondrial Ca content in normal fibers was low, 0.8 --0.5, and there was no evidence of mitochondrial Ca sequestration in muscles frozen after a K contracture lasting 30 min. Transmitochondrial gradients of K, Na, and C1 were small (0.9-1.2). In damaged fibers, massive mitochondrial Ca accumulation of up to 2 mol/kg dry wt in granule form and associated with P could be demonstrated. Our findings suggest (a) that the nonDonnan distribution of CI in smooth muscle is not caused by sequestration in organelles, and that considerations of osmotic equilibrium and electroneutrality suggest the existence of unidentified nondiffusible anions in smooth muscle, (b) that nuclei do not contain concentrations of Na or Ca in excess of cytoplasmic levels, (c) that mitochondria in PAMV smooth muscle do not play a major role in regulating cytoplasmic Ca during physiological levels of contraction but can be massively Ca loaded in damaged cells, and (d) that the in situ transmitochondrial gradients of K, Na, and CI do not show these ions to be distributed according to a large electromotive Donnan force.
منابع مشابه
nonDonnan distribution of CI in smooth muscle is not caused by sequestration in organelles, and that considerations of osmotic equilibrium and electroneutrality suggest the existence of unidentified nondiffusible anions
Electron probe analysis of dry cryosections was used to determine the composition of the cytoplasm and organelles of rabbit portal-anterior mesenteric vein (PAMV) smooth muscle. All analytical values given are in mmol/kg wt --+ SEM. Cytoplasmic concentrations in normal, resting muscles were: K, 611 --1.7; Na, 167 _+ 2.7; C1, 278 -+ 1.0; Mg, 36 --1.1; Ca, 1.9 -+ 0.5; and P, 247 --1.1. Hence, the...
متن کاملElectron probe analysis of vascular smooth muscle. Composition of mitochondria, nuclei, and cytoplasm
Electron probe analysis of dry cryosections was used to determine the composition of the cytoplasm and organelles of rabbit portal-anterior mesenteric vein (PAMV) smooth muscle. All analytical values given are in mmol/kg wt +/- SEM. Cytoplasmic concentrations in normal, resting muscles were: K, 611 +/- 1.7; Na, 167 +/- 2.7; Cl, 278 +/- 1.0; Mg, 36 +/- 1.1; Ca, 1.9 +/- 0.5; and P, 247 +/- 1.1. H...
متن کاملMUSCARINIC RECEPTOR SUBTYPES IN SMOOTH MUSCLE FROM THE BODY OF HUMAN STOMACH
Up to date, there are four pharmacologically characterized subtypes of muscarinic receptors (M1, M2, M3 and M4). In our study we have investigated muscarinic receptor subtypes in smooth muscle layers of human stomach. Isolated preparations of longitudinal and circular muscle layers from human stomach were used. Acetylcholine, bethanechol, carbachol, pilocarpine and AHR -602 produced concen...
متن کاملEffect of New Derivatives of Dihydropyridine on Rat Ileal Smooth Muscle in Vitro
In this research we evaluated the calcium channel antagonist activity of various diester analohues of nifedipine on rat ileal smooth muscle.in these analogues,the orthophenyl group at position 4 was replaced by 1 methyl 2-meythylsulfonyl or methylthio 5-imidazolyl.wistar rats(180-250g) were killed by a blow to the head.the intestine was removed above the ileucecal junction and longitudinal smoo...
متن کاملSEQUESTRATION OF LEUKOCYTES BY THE ISOLATED PERFUSED RAT LUNG
The sequestration of rat leukocytes and bone marrow cells by the lung vasculature was studied using an isolated perfused rat lung preparation. The passage of latex particles of 7.6 µm in diameter and non-hematopoietic cells through the lung blood vessels was also studied. Leukocytes and bone marrow cells were reversibly sequestered from circulation, whereas, latex particles and non-hematop...
متن کامل