4-acetamido-4--isothiocyanatostilbene-2-2--disulfonic-acid and Hypertrophy

Hypertrophy of vascular smooth muscle cells (VSMC) is a pathogenic feature of hypertension which may contribute to abnormal vessel tone and function. As a consequence of the increase in cell size associated with hypertrophy, it is likely that alterations in the mechanisms that regulate VSMC intracellular volume occur. Because the Na+/H+ exchanger plays an important role in volume regulation and because we previously observed long term alterations in Na+/H+ exchange and pHi in response to angiotensin-II-induced (ang II) hypertrophy, we studied cell-acidifying mechanisms. To do this, we measured alkaline recovery from NH4Cl-mediated alkalinization, using the fluorescent dye, 2',7'-bis-(2-carboxyethyl)-5(6)-carboxyfluorescein. VSMC were growth-arrested (0.4% calf serum for 24 h) or hypertrophied (100 nM ang II in 0.4% calf serum for 24 h). Ang II-treated cells exhibited a 107% increase in alkaline recovery over control cells (13.86 +/- 1.87 versus 6.68 +/- 1.01 mmol H+/min/liter cells). The increase in alkaline recovery was not a result of increased Cl-/HCO-3 exchange becaue it was not HCO-3 dependent nor inhibited by 4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid. Studies with bumetanide and the sterically inhibited substrate N(CH3)4+ showed that the alkaline recovery was mediated by NH4+ transport via the Na/K/2Cl cotransporter. Ang II-treated cells exhibited a 334% increase in bumetanide-sensitive alkaline recovery over control cells (9.16 +/- 1.90 versus 2.11 +/- 1.46 mmol H+/min/liter cells). Ang II-treated cells also exhibited a 90% increase in bumetanide-sensitive 86Rb uptake over control cells. These findings demonstrate that Na/K/2Cl cotransport activity is specifically induced in ang II-hypertrophied VSMC and establish this transporter as a component of the hypertrophic growth response.

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; Ammonium Chloride; Animals; Carrier Proteins; Cations; Cells, Cultured; Fluoresceins; Hydrogen-Ion Concentration; Hypertrophy; Male; Muscle, Smooth, Vascular; Rats; Rats, Inbred Strains; Sodium-Potassium-Chloride Symporters

The effects of ion-transport blockers on CCK-8-induced protein output and concomitant fluid secretion were compared in isolated, perfused normal and hypertrophied rat pancreata. In the normal pancreas, perfusion with ouabain (1 mM), amiloride (1 mM), furosemide (1 mM), or SITS (0.1 mM) caused corresponding inhibition of both fluid and protein secretion that was induced by 100 pM CCK-8. Hypertrophy of the pancreas was produced by oral administration of a synthetic protease inhibitor (FOY-305) once a day for 3 wk. In the hypertrophied pancreas, perfusion with ouabain (0.1 or 1 mM) or amiloride (0.1 mM or 1 mM) decreased CCK-8-induced fluid secretion without changing CCK-8-induced protein output. Perfusion with furosemide (1 mM) inhibited both fluid and protein secretion induced by CCK-8, but the amount of inhibition of fluid secretion was much greater than that of protein secretion. Perfusion with SITS (0.1 mM) significantly decreased CCK-8-induced fluid secretion but not protein secretion. These results indicate that in contrast to a normal rat pancreas, the coupling of fluid and protein secretion induced by CCK-8 can be disrupted by experimental procedures that induce hypertrophy in the rat pancreas.

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; Amiloride; Animals; Esters; Furosemide; Gabexate; Guanidines; Hypertrophy; Ouabain; Pancreas; Pancreatic Juice; Perfusion; Rats; Rats, Inbred Strains; Sincalide