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H W Overbeck

Publications and source records attributed to H W Overbeck.

At least 19 recordsLinked to original sources
PubMed1995

Humoral factor(s) in hypertensive rats trophic for cultured aortic smooth muscle cells.

Humoral factors in one-kidney, one-clip (1K,1C) hypertension in rats increase growth of smooth muscle cells cultured from rat arteries. To further characterize the plasma factor or factors involved, we prepared male rats with early, benign 1K,1C hypertension and paired them with one-kidney (1K) normotensive controls. In the presence of growth stimulated by background levels (1%) of fetal calf serum (FCS), plasma-derived serum (PDS), fresh or frozen, from 99 1K,1C rats differentially increased [3H]thymidine incorporation of growth-arrested rat aortic cells; increases were up to 93% more than those evoked by the paired 1K PDS and were concentration related (P < 0.01). However, there was no evidence for a differential effect of 1K,1C PDS in the absence of FCS nor of PDS after boiling. On the other hand, neither treatment of PDS with proteolytic enzymes nor charcoal absorption ablated this differential trophic effect. Thus this study provides evidence that the humoral factor(s) in hypertension are resistant to freezing, proteolysis, and charcoal absorption, but sensitive to boiling, and they require background levels of growth for expression.

Animals↗
PubMed1995

Humoral factors trophic for vascular smooth muscle during the development of hypertension in rats.

There is evidence that a humoral factor or factors in rats with one-kidney, one-clip (1K1C) hypertension increase growth of cultured vascular smooth muscle cells. Such humoral trophic factors may contribute to the abnormal growth of arterial muscle in hypertension. To further study the longitudinal expression of this trophic factor or factors, we prepared rats with 1K1C hypertension of different durations. To determine if the factor or factors are also expressed in other forms of experimental hypertension, we additionally prepared rats with two-kidney, one-clip (2K1C) hypertension and paired two-kidney (2K) normotensive controls; we also studied Spontaneously Hypertensive Rats (SHR) plus appropriate controls. In the presence of growth stimulated by background levels (1%) of fetal calf serum, 20% platelet-poor, plasma-derived serum (PDS) from 1K1C rats 8-14 days (n = 10) and 28 days (n = 12) after clipping increased [3H]-thymidine incorporation of growth-arrested cultured rat aortic smooth muscle cells more than the paired 1K PDS, by up to +67% and +40%, respectively (P < 0.01). However, with PDS from 1K1C rats 4 days (n = 11) and 38 days (n = 6) after clipping there was no evidence for a differential effect (P > 0.5 and P > 0.1, respectively). PDS from seven 2K1C rats (at 9 days) also increased [3H]-thymidine incorporation of the assay cells more than PDS from the paired 2K rats, by up to +19% (P < 0.05). However, there was no evidence that PDS from SHR differentially increased cellular thymidine incorporation. Thus, evidence from this study suggests that the humoral factor or factors trophic for vascular smooth muscle are expressed in both low- and high-renin forms of experimental renovascular hypertension, but not in the very early or in the late complicated stages of the hypertension, or in genetic hypertension in rats.

Animals↗
PubMed1994

Culture of rat mesenteric arteriolar smooth muscle cells: effects of platelet-derived growth factor, angiotensin, and nitric oxide on growth.

We cultured smooth muscle cells as explants from rat mesenteric arterioles (40-200 microns in diameter) obtained by injecting a suspension of iron oxide intraarterially and magnetically separating the arterioles after collagenase digestion of adventitial tissue. In third-passaged cells we ascertained smooth muscle purity of > 98% by characteristic morphology, contraction responses, and specific immunofluorescence staining. Treatment of growth-arrested (in 0.4% fetal calf serum) cells with platelet-derived growth factor (0.3-7.5 nM) or angiotensin II (0.001-1000 nM) induced 3H-thymidine incorporation and cell proliferation in a dose-dependent manner (P < 0.01). S-nitroso-N acetylpenicillamine (0.05-0.5 mM), a nitric oxide-generating compound, inhibited 10% fetal calf serum-induced 3H-thymidine incorporation (P < 0.05) and cell proliferation (P < 0.01). The antimitogenic effect of S-nitroso-N-acetylpenicillamine was significantly reduced by hemoglobin and potentiated by superoxide dismutase (P < 0.01). In addition to a new technique for culturing mesenteric arteriolar smooth muscle cells, these findings provide evidence that platelet-derived growth factor, angiotensin II, and nitric oxide may be involved in their growth control.

Angiotensin II↗
PubMed1994

Plasma-derived serum from hypertensive rats differentially increases growth of cultured arteriolar smooth muscle.

A role for humoral factors in the arterial hypertrophy accompanying hypertension has been suggested, but direct evidence is lacking. We measured [3H]thymidine incorporation of growth-arrested smooth muscle cells, cultured from renal preglomerular arterioles of normal rats and exposed for 12 h to 10% platelet-poor plasma-derived serum (PDS) from male rats with early, benign, one-kidney, one-clip hypertension and paired one-kidney normotensive control rats. In the presence of low background concentrations (1-2%) of fetal calf serum, PDS from hypertensive rats increased [3H]thymidine incorporation up to 117% more than PDS from normotensive rats (P < 0.0001). Results were similar for the < 10,000 mol wt fraction of PDS and for PDS from rats drinking saline vs. water or eating a 7% (high) vs. a 0.45% NaCl diet. PDS from hypertensive rats also differentially increased smooth muscle cell proliferation and c-fos mRNA expression. Platelet-derived growth factor levels in PDS were undetectable (< 0.17 ng/ml). This study provides evidence for altered concentrations of sodium chloride-unresponsive plasma factor or factors in hypertension that result in enhanced growth of arteriolar smooth muscle cells.

Animals↗
PubMed1992

Culture of renal arteriolar smooth muscle cells. Mitogenic responses to angiotensin II.

We cultured smooth muscle cells from rat renal preglomerular arterioles by injecting a suspension of iron oxide into the left ventricle, separating the arterioles magnetically, and growing cells from explants. In passaged cultures we ascertained vascular smooth muscle purity of > 98% by morphology; contraction to norepinephrine and angiotensin; positive immunofluorescence staining through the sixth passage with monoclonal antibodies to smooth muscle-specific alpha- and gamma-isoactins, myosin, and desmin; and the absence of von Willebrand factor. Angiotensin II (10(-12)-10(-5) M) induced dose-dependent DNA synthesis and proliferation of subcultured (three times) arteriolar smooth muscle cells from a growth-arrested state (p < 0.01). Angiotensin II (10(-5) M) also induced the cells to express c-fos mRNA. We find no previous report of culture of smooth muscle cells from renal preglomerular arterioles. Our findings also provide evidence that angiotensin II is mitogenic to arteriolar muscle cells and thus may be involved in their hyperplasia accompanying hypertension.

Angiotensin II↗
PubMed1991

Pressure-independent arteriolar rarefaction in hypertension.

To assess the role of pressure in the arteriolar rarefaction associated with hypertension, we studied microvascular density in a hindquarters muscle (cremaster) of rats, 8 wk after coarctation (n = 8) or sham-coarctation (n = 10) of the abdominal aorta. To document the level of arterial pressure in hindquarters vascular beds of similar rats 8-9 wk after initial surgery, we implanted femoral arterial catheters under anesthesia and, 2-5 days later, we measured conscious femoral arterial pressures in coarcted [93 +/- 4 (SE) mmHg; n = 7] and sham-coarcted (110 +/- 3 mmHg; n = 4) rats. The cremaster muscle microcirculation was examined after fixation and Microfil infusion at in vivo pressures. The density of distal third- to fourth-order arterioles was lower by 19% (P = 0.03) in coarcted (1.37 +/- 0.06 mm/mm2) than in sham-coarcted (1.69 +/- 0.11 mm/mm2) rats. We conclude that pressure-independent mechanisms are involved in the arteriolar rarefaction accompanying hypertension.

Animals↗
PubMed1990

Digitalis attenuates arterial hypertrophy in experimental hypertension.

Several investigators have reported that digitalis administration reduces cardiac hypertrophy in rats with experimental hypertension. To determine whether digitalis similarly affects growth of arteries, we studied young (5- to 14-week-old), male, one-kidney, one-clip hypertensive rats (1K1C; n = 14) and one-kidney normotensive control rats (1K; n = 26). Half of the rats received digoxin (150 mg/kg body wt/day) in chow starting 1-2 weeks before clipping (1K1C-D; 1K-D); the other half were pair-fed (1K1C-C; 1K-C). Serum digoxin levels averaging 488 ng/ml were documented in rats receiving digoxin. After 3-5 weeks of hypertension (conscious tail blood pressures), and at a similar time period in normotensive control rats, we measured direct femoral arterial pressure and weighed standardized segments of the thoracic aorta. At sacrifice body weights of the four groups did not differ. In the one-kidney control rats, mean +/- SE femoral arterial pressure (1K-D, 108 +/- 3; 1K-C, 111 +/- 4, mm Hg), thoracic aortic dry weight (1K-D, 36.6 +/- 0.6; 1K-C, 36.2 +/- 1.1. mg/kg body wt), and aortic water content (1K-D, 62.7 +/- 0.4; 1K-C, 62.4 +/- 0.4, % wet weight) did not differ between rats receiving or not receiving digoxin, respectively. As compared with pooled normotensive control rats, femoral arterial pressure (1K1C-D, 165 +/- 8; 1K1C-C, 153 +/- 5), aortic water content (1K1C-D, 64.8 +/- 0.4; 1K1C-C, 64.9 +/- 0.5), and aortic weight (1K1C-D, 44.8 +/- 2.1; 1K1C-C, 50.1 +/- 1.6) were increased (P less than 0.001) in the one-kidney, one-clip rats, on or off digoxin. Comparison of hypertensive rats receiving to those not receiving digoxin revealed no differences in arterial pressure or aortic water content, but aortic growth was significantly attenuated (-41%, P = 0.02) in the hypertensive rats receiving digoxin. These results provide evidence that digoxin reduces hypertensive arterial growth by a mechanism that does not affect normal growth.

Animals↗
PubMed1989

Aortic hypertrophy and "waterlogging" in the development of coarctation hypertension.

To study the mechanisms and roles of vascular structural changes during the development of hypertension, we coarcted or sham-coarcted the abdominal aorta of rats. At intervals of 3 to 56 days later, we obtained standardized segments of thoracic and abdominal aortas for measurement of dry weight, water content, and amino acid content. Carotid arterial pressure was elevated by day 5 in coarcted rats and remained elevated. Femoral and tail arterial pressures remained normal. Cardiac ventricular weight and dry weight of the thoracic aorta, normalized for body weight, rose rapidly over 3-10 days in coarcted rats, remaining constant at 50-60% above levels in sham-coarcted rats thereafter. In contrast, water content of thoracic aorta in coarcted rats peaked at 123% of control values on day 7 (p less than 0.001), falling rapidly thereafter to levels about half of peak. Increments in dry weight and water content of the normotensive abdominal aortic segments were of far lesser magnitude and occurred 1 to 2 weeks later, probably reflecting the effects of initial hypotension of the hindquarters. Percent hydroxyproline of intima-media segments of the thoracic aorta remained normal during the 8-week period, indicating that increases in aortic dry weight did not represent disproportional fibrosis and thus are attributable to muscular hypertrophy. These results provide support for the hypothesis that arterial wall "waterlogging" is primarily an early manifestation of the hypertensive process. The greatest magnitude of waterlogging coincides with the rapid early increase in aortic dry weight, representing hypertrophy, which suggests common mechanisms, such as activation of Na+-H+ antiport.

Amino Acids↗
PubMed1988

Bioassay by cross-perfusion for circulating inotropic factor in hypertension.

To study inotropic effects of blood from one-kidney, one-clip (1K,1C) rats with early (less than 7 days) or chronic (greater than 4 wk) benign hypertension, we assessed arteriolar resistance and norepinephrine (NE) responses in vascularly isolated, innervated assay hindlimb vascular beds of alpha-chloralose-anesthetized, normal male recipient rats. Hindlimbs were cross-perfused (2 ml/min) with blood from anesthetized donor rats with limb outflow returned to the donor rat. Perfusion pressure was monitored. Complete NE (injected intra-arterially) dose-response curves in limbs perfused with donor blood from nine early 1K,1C rats, compared with nine appropriate normotensive control donor rats, indicated unchanged thresholds, 50% effective doses, and maximal responses. Curves in limbs perfused with blood from 10 chronic 1K,1C, compared with 10 appropriate controls, suggested small (P less than 0.02) leftward shifts. Decreases (P less than 0.01) in maximal responses were also observed. Limb resting resistance and minimal resistance (sodium nitroprusside) did not rise, even after 4-5 h of cross-perfusion. These results provide no evidence in early 1K,1C and little evidence in chronic 1K,1C that humoral factors, including ouabainlike inhibitors, evoke physiologically significant inotropic effects in arterioles in vivo.

Algorithms↗
PubMed1988

Hypertensive dog plasma inhibits the Na+-K+ pump of cultured vascular smooth muscle.

We investigated the effects of plasma from dogs with perinephritic hypertension on the Na+-K+ pump of cultured dog vascular smooth muscle cells. We also measured [3H]ouabain binding by myocardium and vascular tissue. Fresh, unprocessed plasma from healthy dogs during the first 6 weeks of benign one-kidney, one wrapped hypertension and from paired normotensive control dogs was layered over confluent primary cultured puppy aortic smooth muscle cells that had been sodium-loaded with monensin. In 26 paired assays of plasma from four pairs of dogs, cells incubated in the presence of plasma from hypertensive dogs had significantly reduced total (p less than 0.01) and ouabain-sensitive (p less than 0.001) 86Rb+ uptakes, but their intracellular sodium content did not differ from cells incubated in paired normotensive plasma. We no longer detected these uptake differences when passaged cells or cells cocultured with bovine endothelial cells were used for assay or when plasma was treated with protease inhibitors or boiled. However, boiled plasma increased the sodium content of the assay cells, suggesting an ionophorelike effect. Levels of pump inhibitory activity in plasma appeared to remain constant during Weeks 1 to 6 of hypertension. We found no evidence for altered numbers of pump sites in cardiovascular tissues from these hypertensive dogs. These findings support the hypothesis that plasma factors inhibit the membrane Na+-K+ pump in vascular smooth muscle cells in this form of hypertension. These plasma inhibitory factors apparently do not induce pump molecules.

Animals↗
PubMed1988

Morphometric evidence for non-pressure-related arterial wall thickening in hypertension.

To investigate the relation of pressure and vascular wall thickening in hypertension, we coarcted the abdominal aorta upstream to the renal arteries in 14 rats. Sham-coarcted (n = 16) and two-kidney, one-clip (Goldblatt) hypertensive rats (n = 13) served as controls. Tail, femoral, and carotid arterial pressures rose (p less than 0.01) in the two-kidney, one-clip hypertensives; only carotid pressure rose (p less than 0.01) in the coarcted rats, tail and femoral pressures remaining normal (p greater than 0.25). Thus, the hindquarters of the coarcted rats remained normotensive. Four to six weeks after surgery we perfusion-fixed vascular tissues of the hindquarters, including kidneys, with formalin at in vivo levels of pressure. Glycol methacrylate-embedded tissues were sectioned at 1 micron thickness and vessels quantitatively evaluated. The outer medial and lumen perimeters of abdominal aorta, femoral artery, and renal arterioles were measured; from these measurements, vessel outer and lumen diameters, medial thickness, medial area, and medial thickness-to-lumen radius ratios were calculated. Compared with sham-coarcted rats, abdominal aorta, femoral arteries, and renal arterioles less than 61 microns outer diameter in rats with coarctation and Goldblatt hypertension had significantly increased (up to +100%) medial area, medial thickness, and medial thickness-to-lumen radius ratios. In general, magnitudes of abnormalities were similar in Goldblatt and coarcted rats. Renal arterioles greater than 60 microns outside diameter in Goldblatt hypertensive, but not coarcted, rats also were thickened. These results indicate that vascular wall thickening occurs in conduit arteries and smaller renal arterioles in the normotensive hindquarters of coarcted rats, providing morphometric evidence for non-pressure-related mechanisms involved in vascular growth in this form of hypertension.

Animals↗
PubMed1988

Arteriolar wall thickening in hypertensive rats unrelated to pressure or sympathoadrenergic influences.

We have previously reported that experimental aortic coarctation in rats is accompanied by non-pressure-related increases in the wall-to-lumen ratio (W/L) of cremaster arterioles. To investigate the role of the sympathoadrenergic system in this arteriolar wall thickening, we partially constricted or sham-constricted the abdominal aorta in adrenal-demedullated, 6-week-old rats that had had guanethidine injections to produce peripheral sympathectomy (S rats, n = 17 coarcted, 16 sham-coarcted) and in sham-demedullated, sham-sympathectomized control rats (SS rats, n = 13 coarcted, 15 sham-coarcted). In both SS and S rats with coarctation, tail and femoral arterial and conscious abdominal aortic pressures were not increased but carotid pressures rose by greater than 30% (p less than 0.01), accompanied by 46-75% increases in cardiac ventricular weight/body weight. In coarcted rats, 4-6 weeks after aortic constriction, compared with sham-coarcted rats, whether S or SS, observation of the cremaster microcirculation revealed increased wall area, wall thickness, and W/L of third- to fifth-order arterioles, both in the resting state and after maximal relaxation with topical nitroprusside. For example, in coarcted S rats wall area after nitroprusside was elevated by 24%, 39%, and 37% in third-, fourth-, and fifth-order arterioles (p less than 0.01). These findings indicate that arteriolar wall thickening in hypertension may occur independently of intra-arterial pressure or sympathoadrenergic influences. Humoral growth factors may be involved.

Animals↗
PubMed1987

Decreased intraocular pressure in dogs with one-kidney, one wrapped hypertension.

We examined the relationship of intraocular pressure and the development of one-kidney, one wrapped (perinephritic) hypertension in the dog. Conscious femoral arterial pressure (direct arterial puncture) and intraocular pressure (Schiotz tonometer) were measured weekly before and after the surgical induction of hypertension in 11 healthy male mongrel dogs and before and after unilateral nephrectomy in 15 normotensive control dogs. Preoperative mean arterial pressure (102 +/- 5 vs 99 +/- 8 [SD] mm Hg, hypertensive vs control dogs) and intraocular pressure (18.1 +/- 2.5 vs 17.7 +/- 2.1 mm Hg, hypertensive vs control dogs) were similar in both groups. In normotensive control dogs, mean arterial pressure and intraocular pressure averaged over the postoperative period (4-8 weeks) did not differ significantly from preoperative values. In contrast, during the same period arterial pressure significantly increased and intraocular pressure significantly decreased in hypertensive dogs (arterial pressure, 163 +/- 8 mm Hg; intraocular pressure, 11.9 +/- 4.0 mm Hg; p less than 0.001 for both values compared with corresponding values in control dogs). Intraocular pressure was inversely related to arterial pressure in hypertensive dogs (r = 0.56, p less than 0.01). These observations indicate that intraocular pressure decreases with the development of canine one-kidney, one wrapped hypertension. The mechanism of this decrease may be related to abnormalities in Na+,K+-adenosine triphosphatase activity found in this form of hypertension.

Animals↗
PubMed1987

The vascular Na+-K+ pump in experimental hypertension.

We assessed the role of putative circulating ouabainlike factor(s) on in vivo arteriolar function in rats with very early (less than 7 days; mean, 3 days) and chronic (greater than 4 weeks) benign, one-kidney, one clip (1K1C) hypertension. Thus, we measured vascular responses in vasodilated (nitroprusside or adenosine), vascularly isolated, innervated hindlimb vascular beds of chloralose-anesthetized 1K1C rats perfused with their own blood at 1 ml/min. Complete norepinephrine dose-response curves in 8 rats with chronic and 28 with early 1K1C hypertension, compared with appropriate normotensive control rats, showed unchanged thresholds and ED50 values. Magnitude of ouabain-induced leftward shifts of the norepinephrine dose-response curve in 18 rats with chronic and 21 with early 1K1C hypertension, compared with appropriate normotensive control rats, was unchanged. Blockade of neural uptake of norepinephrine by desimipramine (10(-7) M) in 8 1K1C rats did not alter these results. These findings provide no evidence in this form and these stages of hypertension that humoral ouabainlike inhibitors of the Na+-K+ pump evoke physiologically significant inotropic effects in arterioles in vivo. It is possible, however, that induction of vascular Na+-K+-adenosine triphosphatase by circulating inhibitors modified the vascular responses to norepinephrine and ouabain in these rats.

Animals↗
PubMed1986

Myocardial Na, K-ATPase in one-kidney, one-clip hypertensive rats.

Myocardial ventricular Na, K-ATPase activity of normotensive rats was compared with that of healthy rats with chronic benign one-kidney, one-clip hypertension. The yield of protein (mg/g wet wt left plus right ventricles) in microsomal and sarcolemmal membrane fractions was the same for both normotensive and hypertensive rat ventricles. However, the yield of protein (mg/ventricle) was 26% greater in the hypertensive relative to the normotensive animals, consistent with the presence of hypertrophy, as also indicated by an increase in the ratio of ventricular to body weight and a shift in the isomyosin composition. Na, K-ATPase activity, sodium-dependent phosphorylation and ouabain binding were significantly (P less than 0.05) decreased (by 20%, 40%, and 45%, respectively) in the hypertensive rat ventricles when the data were expressed in units/g tissue wet weight. However, when expressed in units per ventricle, values in normotensive and hypertensive animals were similar. The molecular activity or turnover number of ventricular (and also renal) Na, K-ATPase activity was the same in both groups of animals. These results suggest that the decrease in myocardial specific Na, K-ATPase activity in the rat made hypertensive by removing one kidney and constricting the renal artery of the other kidney is related to the presence of cardiac hypertrophy.

Animals↗
PubMed1986

Effect of hypertensive rat plasma on ion transport of cultured vascular smooth muscle.

We layered fresh, unprocessed plasma from healthy rats with early (less than or equal to 7 days) or benign, chronic (greater than 3 wk) one-kidney, one-clip hypertension and from paired one-kidney normotensive control rats over confluent primary-cultured rat aortic smooth muscle cells. Plasma from all rats increased cellular ouabain-sensitive 86Rb+ uptake and sodium content and decreased ouabain-insensitive 86Rb+ uptake compared with uptakes and content in the presence of balanced salt solution (P less than 0.01). Cells incubated in the presence of plasma from rats with early (P less than 0.02) or chronic hypertension (P less than 0.01) had significantly reduced ouabain-sensitive 86Rb+ uptake when compared with cells incubated in normotensive plasma, but their intracellular Na+ contents were not lower. We no longer detected this uptake difference when chronic hypertensives drank 0.9% NaCl instead of water. Plasma from hypertensive rats also altered ouabain-insensitive 86Rb+ uptake by the cultured cells. These findings of this new, reproducible, and specific assay system support the hypothesis that plasma factors inhibit the membrane sodium-potassium pump in vascular smooth muscle cells in this form of hypertension. The abnormality occurs in both early and chronic stages, but may not be related to sodium intake. The data also provide evidence for plasma factors in hypertension altering membrane K+ permeability.

Animals↗
PubMed1986

Vascular smooth muscle membrane potential in rats with early and chronic one-kidney, one-clip hypertension.

It has been suggested that the cell membrane of vascular smooth muscle in one-kidney, one-clip hypertension, and other forms of volume-dependent, low-renin hypertension, is partially depolarized due to the effects of a circulating ouabain-like factor, and that this depolarization is an important mechanism of the hypertension. Levels of circulating ouabain-like factors in early stages of volume-dependent hypertension are reported equal to, or greater than, those in chronic hypertension. Therefore, we measured intracellular membrane potential (Em) in vitro (37 degrees C, physiological salt solution) in vascular smooth muscle of the caudal artery from normotensive control rats (1K) and rats in the early and chronic stages of one-kidney, one-clip hypertension (1K1C). In 20 chronic 1K1C (4-6 weeks of systolic pressure greater than 140 mm Hg) the resting Em's (M +/- SEM) were -46.7 +/- 0.7 mV, compared to -50.9 +/- 0.6 for 20 1K (P less than 0.01). The delta Em due to 1 mM ouabain was attenuated in 10 1K1C compared to 11 1K (+5.4 +/- 0.9 and +10.0 +/- 0.7 mV, respectively; P less than 0.01). The Em's of the two groups after ouabain were the same. In contrast, in 16 early 1K1C rats (less than 7 days hypertension, average 3 days) compared to 15 appropriate 1K, there were no significant alterations in resting Em (-50.1 +/- 0.4 mV, compared to -50.5 +/- 0.5, respectively) and there were no differences in ouabain response. These results suggest a temporal dissociation between levels of humoral inhibitors and depolarization, and between depolarization and hypertension, and thus fail to support the hypotheses that there are casual relationships between these variables in volume-dependent, low-renin hypertension.

Animals↗