Biomedical subjects

M K Hise

Publications and source records attributed to M K Hise.

32 records · Page 2Linked to original sources

PubMed1989

Epidermal growth factor receptor regulation in rat kidney: two models of renal growth.

The binding of 125I-labeled epidermal growth factor (EGF) to plasma membranes prepared from rat kidney cortex was studied following unilateral nephrectomy, a model of proximal tubule cell hypertrophy, and following the administration of folic acid, a model of proximal tubule cell hyperplasia. Binding of 125I-EGF was a linear function of basolateral membrane protein content and time of incubation. Specific binding to luminal brush-border membranes was not evident in these studies. Neither insulin nor insulin-like growth factor I could displace EGF binding, indicating that binding was specific. Scatchard analysis revealed a single binding site. The KD in sham-operated animals 48 h after surgery was 11.2 +/- 1.4 nM, whereas Bmax averaged 95.2 +/- 4.1 fmol/mg protein (n = 3). Similar values were obtained in nephrectomized animals. The Bmax of folic acid-untreated animals averaged 212.5 +/- 6.9 fmol/mg 48 h after administration, whereas that of vehicle-injected controls averaged 85.4 +/- 9.2 (n = 3, P less than 0.001). Differences in binding were not related to changes in affinity, ligand degradation by the preparations, or receptor binding of endogenous EGF. These data indicate that regeneration following folic acid administration is associated with an upregulation of proximal nephron EGF receptors that may play an important role in the mitogenic response.

Animals↗

PubMed1988

Activity of calcium/phospholipid dependent protein kinase during rat kidney development.

The activity of the calcium sensitive phospholipid dependent protein kinase C (PKC) was studied in cytosol and in the proximal tubular luminal membrane of rats during growth. Cytosolic activity was elevated at 14 and 21 days of age and fell to adult levels by day 60. Luminal brush border membrane activity on the other hand was low on day 14 but reached adult levels by day 21. Changes in brush border membrane PKC activity may have important consequences for the development of electrolyte transport in proximal tubular cells.

Alkaline Phosphatase↗

PubMed1988

Characterization and localization of calcium/phospholipid-dependent protein kinase-C during diabetic renal growth.

The substrate specificities of calcium/phospholipid-dependent kinase-C (PKC) were examined in rat kidney cortex, and localization of the protein was studied after the induction of diabetes. The cytosolic kinase was eluted from an anion exchange resin using a linear gradient of 0-0.15 M NaCl. A sharp peak of activity was demonstrated at approximately 80 mM using histone as a substrate. The kinase demonstrated a broad pH optimum of 6.5-8.0. ATP was the preferred phosphorus donor. The Ka for ATP averaged 2.6 +/- 0.1 microM (n = 4) and was not different in diabetic animals. Lysine-rich histones, but not arginine-rich or mixed histones, were the most suitable phosphorus acceptors. Phosphatidylserine stimulated kinase activity with Ka of 4.5 +/- 0.7 microM in the presence of 20 microM diolein (n = 3). Twenty micromolar diolein in the presence of 25 microM phosphatidylserine lowered the apparent Ka for calcium from 17.2 +/- 1.4 to 3.3 +/- 1.5 microM (n = 3; P less than 0.01). Similar data were evident in diabetic animals. Diabetic renal growth was induced by the injection of streptozotocin (35 mg/kg, iv). At the end of 4 weeks, blood glucose averaged 119.6 +/- 7.4 mg/dl in vehicle-injected controls and 548.7 +/- 21.6 mg/dl in diabetic animals (n = 5; P less than 0.001). Despite reduced weight gains in diabetic animals, renal protein content was increased in this group compared to the control value. Neither cytosolic nor proximal tubule basolateral membrane PKC activity changed after the induction of diabetes; however, luminal brush border PKC activity increased from 83.8 +/- 4.6 pmol/mg.min in control animals to 107.3 +/- 55 pmol/mg.min in diabetic animals (n = 5; P less than 0.02). The increased activity in the brush border membrane may have important consequences for the growth response of the kidney in diabetes.

Animals↗

PubMed1986

Lipid methylation, sodium transport and the response to PTH in renal tubules.

The possible role of progressive methylation of phosphatidylethanolamine to phosphatidylcholine on sodium transport was examined in a suspension of rabbit proximal convoluted tubules. The relation between progressive methylation and the action of parathyroid hormone on sodium transport in this nephron segment was also determined. Incubation of the suspended tubules for 10 minutes at 37 degrees C with 200 microM S-adenosyl-L-[3H]-methyl methionine, a methyl donor, revealed a significant rate of de-novo phosphatidylcholine synthesis. The inactive adenosine analogue, 3-deazaadenosine (DZA), had a significant inhibitory effect on lipid methylation. Despite the inhibition of methylation by DZA, the ouabain sensitive component of oxygen consumption, an index of sodium transport, was not affected. PTH significantly inhibited ouabain sensitive oxygen consumption but had no effect on the methylation of phosphatidylethanolamine. Inhibition of methylation by DZA, did not affect the inhibitory effect of PTH on oxygen consumption. These studies demonstrate that in the proximal convoluted tubule of the rabbit the progressive methylation pathway is present and that inhibition of this pathway does not affect sodium transport. In addition, these studies suggest that the inhibitory effect of PTH on sodium transport is not mediated by the methylation pathway.

Animals↗

PubMed1986

Physical properties of the rat renal brush border membrane during growth.

The biophysical properties of rat renal brush border membranes were examined during neonatal development and following unilateral nephrectomy by sensitive fluorescence techniques. Differences in the fluorescence anisotropy of 1,6 diphenyl-1,3,5-hexatriene (DPH) following unilateral nephrectomy were not apparent; by contrast, the luminal membrane becomes more rigid as animals age. Although growth of the kidneys is common to both states examined, fundamental differences are apparent at the level of the luminal membrane.

Acid Phosphatase↗

PubMed1986

Fatty acyl chain composition in the determination of renal membrane order.

The relative roles of phospholipid fatty acyl chain length and phospholipid fatty acyl chain unsaturation in the determination of rat renal brush border membrane order were examined using multilamellar liposomes. Exposure of brush border membranes to sphingomyelinase resulted in a time- and concentration-dependent decrement in sphingomyelin content. Liposomes prepared from lipid extracts of these membranes were reconstituted to defined phosphatidylcholine (PC)/sphingomyelin (SPH) ratios with pure synthetic PCs of defined chain length and degrees of unsaturation. Mixed-acid PCs from bovine liver, egg, and the rat renal brush border membrane were also examined. The steady state fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene (DPH) at 37 degrees C was used to reflect acyl chain packing. The steady state anisotropy of DPH in liposomes isolated from the rat renal brush border membrane averaged 0.205 +/- 0.001, n = 8. When liposomes were reconstituted to PC/SPH ratios of 1.1, 1.6, and 2.4 with saturated PCs of acyl chain length 16 to 22, differences in anisotropy between groups were not observed. However, when PCs containing unsaturated or mixed-acid fatty acyl chains were introduced, anisotropy decreased in a concentration dependent fashion. These data suggest that phospholipid fatty acyl chain unsaturation, but not acyl chain length, has a powerful influence on renal brush border membrane order and the PC/SPH ratio is an important determinant of renal membrane order by virtue of the unsaturated fatty acids normally present with these phospholipids.

Animals↗

PubMed1985

Parathyroid hormone and dibutyryl cAMP inhibit Na+/H+ exchange in renal brush border vesicles.

Parathyroid hormone (PTH) and cAMP inhibit sodium, water, and bicarbonate reabsorption in the proximal tubule. We wished to determine whether these agents directly inhibit proximal tubular Na+/H+ exchange. A suspension of rabbit proximal tubules was prepared by enzymatic digestion and Ficoll gradient centrifugation. Oxygen consumption at 37 degrees C was stable over 60 min, averaged 20 nmol X mg protein-1 X min-1, and was inhibited 60% by ouabain. Over 96% of cells excluded trypan blue. From this suspension, brush border membrane vesicles were isolated. The vesicles were enriched 12.7 times in alkaline phosphatase relative to a cortical homogenate and demonstrated pH gradient-stimulated, amiloride-sensitive Na+/H+ countertransport and sodium-phosphate and sodium-D-glucose cotransport. When the tubule suspension was exposed to PTH or dibutyryl cAMP, the activity of Na+/H+ countertransport in the resultant brush border vesicles was inhibited. Neither PTH nor dibutyryl cAMP affected the amiloride-insensitive component of sodium transport or sodium-phosphate or sodium-D-glucose cotransport. The effect of PTH on Na+/H+ counter-transport could not be explained by an alteration in fluidity of the brush border membrane. These experiments demonstrate that PTH and dibutyryl cAMP directly inhibit Na+/H+ countertransport in the brush border membrane of the rabbit proximal tubule.

Amiloride↗

PubMed1985

Relationship among parathyroid hormone, cAMP, and calcium on proximal tubule sodium transport.

Parathyroid hormone (PTH), through the generation of cAMP, inhibits the transport of sodium, bicarbonate, and water in the proximal convoluted tubule. The present studies were designed to determine whether the response to PTH or dibutyryl cAMP by proximal renal tubules requires an influx of calcium into the cells or an alteration in the cytosolic concentration of calcium. O2 consumption was determined in an enriched suspension of rabbit proximal convoluted tubules, and the ouabain-sensitive component of O2 consumption was taken as a measure of sodium transport. PTH (1 IU/ml) inhibited the ouabain-sensitive component of O2 consumption from 14.2 +/- 1.6 to 8.9 +/- 1.1 nmol O2 X min-1 X mg protein-1 (P less than 0.005). Dibutyryl cAMP (10(-4) M) inhibited ouabain-sensitive O2 consumption from 12.0 +/- 1.1 to 8.4 +/- 0.8 nmol O2 X min-1 X mg protein-1 (P less than 0.005). In the presence of lanthanum (5-50 microM) or verapamil (20-200 microM), PTH inhibited ouabain-sensitive O2 consumption by 21.3 +/- 3.4% (P less than 0.025) and 33.9 +/- 5.5% (P less than 0.025), respectively. Dibutyryl cAMP inhibited the ouabain-sensitive O2 consumption by 22.6 +/- 7.1% (P less than 0.025) in the presence of lanthanum and 35.4 +/- 3.1% (P less than 0.01) in the presence of verapamil. To more directly assess the cytosolic concentration of calcium, the fluorescent intensity of quin 2-loaded tubules was determined. As compared with timed controls, exposure to PTH resulted in a lower cytosolic concentration of calcium over the 10 min of incubation. Dibutyryl cAMP had a similar effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Aminoquinolines↗

PubMed1984

Regulation of de novo phosphatidylcholine biosynthesis during renal growth.

Potential regulatory steps of de novo renal cortical synthesis of phosphatidylcholine (PC) were investigated during renal growth in rats. Twenty-four hours following unilateral nephrectomy, cortical PC content was increased in the remaining kidney when compared with sham-operated controls, 3.47 +/- 0.07 and 2.79 +/- 0.14 mumol/mg DNA, respectively (P less than 0.02). No alterations occurred in the cortical PC precursor pools of choline, phosphocholine, cytidine diphosphocholine, or diacylglycerol. At 15 min after the injection of 32P, the incorporation of isotope into the PC pool was increased in the contralateral kidney when compared with sham-operated controls. The calculated maximal velocities of choline kinase and cholinephosphotransferase were increased subsequent to unilateral nephrectomy, supporting a regulatory role for these enzymes in PC biosynthesis during renal growth.

Animals↗

PubMed1984

Fluidity and composition of brush border and basolateral membranes from rat kidney.

The physical state of rat renal brush border and basolateral membranes was examined using the technique of electron spin resonance. As estimated from the order parameters of both 5- and 12-doxyl spin-labeled phosphatidylcholine, the brush border membrane was significantly more ordered than the basolateral membrane. To confirm these findings, fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene was studied. Fluorescence anisotropy at 25 and 37 degrees C was significantly greater in the brush border membrane when compared with the basolateral membrane. The relative contribution of the lipid component to this difference was examined using multilamellar liposomes prepared from lipid extracts of these membranes. Fluorescence anisotropy in the brush border membrane lipids was significantly greater than that in the basolateral membrane lipids at both 25 and 37 degrees C. Compositional determinants of fluidity were examined in both membranes. Factors that may contribute to the more fluid state of the basolateral membrane include 1) a greater lipid-to-protein ratio; 2) a greater ratio of phosphatidylcholine to sphingomyelin; and 3) a tendency toward shorter-length fatty acyl chains.

Animals↗

PubMed1984

Effect of cAMP and calmodulin inhibitors on water absorption in rat proximal tubule.

The possible role of calmodulin in solute transport was examined in the kidney of the rat. Utilizing a radioimmunoassay, calmodulin was identified and quantitated in homogenates of the cortex of the kidney. The physiologic significance of these findings was examined utilizing in vivo microperfusion techniques applied to the proximal convoluted tubule of the thyroparathyroidectomized rat. The addition of dibutyryl cyclic adenosine monophosphate (cAMP) to the luminal perfusion solution resulted in a lower rate of water absorption of 1.67 +/- 0.09 nl min-1 mm-1 as compared to 2.46 +/- 0.11 in controls. The addition of either of two compounds with affinity for calmodulin, trifluoperazine (TFP) or W-13, reversed the cAMP-induced inhibition of water absorption. In the absence of cAMP, neither agent affected water absorption. Analogs of TFP and W-13 with lower binding affinities for calmodulin had no effect on water absorption and did not reverse the cAMP effect. None of the above experimental maneuvers affected the absorption of phosphate. These results demonstrate the presence of calmodulin in the kidney of the rat and suggest that calmodulin may be involved in cAMP-associated inhibition of water and electrolyte transport in the proximal tubule of the rat.

Absorption↗

PubMed1983

Determination of intracellular choline levels by an enzymatic assay.

A sensitive enzymatic assay for the measurement of intracellular choline is described. The separation of choline from choline-containing phospholipids is accomplished by a minor modification of the Folch technique. The method is based on the specific oxidation of choline by choline oxidase. Phenol and 4-aminoantipyrine in the presence of hydrogen peroxide generated by the oxidation of choline and peroxidase form a red quinone dye which can be detected spectrophotometrically. The assay was useful between 12.5 and 100 nanomoles of choline. The recovery of standard choline in liver homogenates averaged 102 +/- 1.6%. Structurally similar compounds produced minimal interference.

Alcohol Oxidoreductases↗

PubMed1983

Renotrophic factors in urine.

Our previous observations of increased renal protein synthesis in rats subjected to the constant intravenous reinfusion of half their urine output has suggested that the circulatory retention of renotrophic factors in urine is capable of stimulating renal growth. In the present studies, using this same model of "half-urine-reinfusion," which is designed to produce a selective halving of renal excretory function, we have demonstrated significant increases in total DNA content and the incorporation of tritiated thymidine in renal DNA. In addition, a bioassay method was developed in which an assay rat, given an intravenous infusion of urine from another rat, exhibited increases in the incorporation of thymidine into renal DNA and the incorporation of radiolabelled choline into renal phospholipid. This renotrophic activity in the urine was only minimally decreased by heating to 100 degrees C for 30 min and was confined to ultrafiltration fractions retained on a membrane with a nominal 10,000-dalton solute rejection. Removal of one kidney from the rats from which the urine was obtained led to only a modest and transient reduction in the excretion of renotrophic activity, suggesting that the urinary renotrophic factors are of circulatory, not renal, origin. Isolated renal cortical fragments incubated with an ultrafiltration retentate of urine displayed a dose-dependent increase in choline incorporation into phospholipid, suggesting a direct action of the factors on kidney tissue. Finally, no evidence of stimulation of either DNA or phospholipid synthesis could be seen in hepatic tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

The inevitability of renal function loss in patients with hypercreatinemia.

UNLABELLED: Although it is anticipated that most patients with renal insufficiency will progress towards end-stage renal disease (ESRD) there have been few population-based studies to validate this assumption. We examined serial creatinines from 3,874 anonymous patients at an urban VA medical center who had a baseline creatinine of 1.4 mg/dl or greater to estimate the frequency of deterioration in renal function (DRF). DRF was defined as the first Cr (1stCr) value being lower than the last Cr (LCr) for each patient. The median follow-up was 48.3 +/- 0.5 months with 18 +/- 0.5 creatinine values per patient. The median 1stCr was 1.6 +/- 0.1 mg/dl with 32.2% of the patients having a 1stCr greater than or equal to 1.7 mg/dl. In the study group, 1,723 (44.4%) had DRF including 1,089 (41.4%) of those patients with a 1stCr of 1.4-1.7 mg/dl. However, 45 (36.6%) of those with a 1stCr value 3.0-5.0 mg/dl did not have DRF, the percent with stable creatinine in this group did not vary with length of follow-up. Over the study period, 299 (7.7%) of all the patients had a creatinine rise to 7.0 mg/dl, with 104 (4%) of those with a 1stCr of 1.4-1.7 mg/dl reaching this endpoint. CONCLUSION: A majority, but not all, patients with renal insufficiency lose renal function over time and those with even mild hypercreatinemia are at risk for deterioration in renal function. Hypercreatinemia, however, does not accurately discriminate between those renal insufficiency patients who are stable versus those at high risk for ESRD.

Analysis of Variance↗