RESUMEN
The purpose of this study was to examine the effects of ginseng extract ingestion on physiological responses to intense exercise. Subjects performed a control ride (CN) on a cycle ergometer, followed by placebo (PL) and ginseng (GS) treatments. Ginseng was ingested as 8 or 16 mg/kg body weight daily for 7 days prior to trial GS. Venous blood was sampled for FFA, lactate, and glucose analyses. Due to similar findings for both dose groups, the subjects were considered as one group. Lactate, FFA, VO2, VE, and RPE increased significantly from 10 through 40 min. RER increased during the first 10 min of exercise and then remained stable, with no intertrial differences. Glucose did not vary significantly from 0 to 40 min or among treatments. RPE was significantly greater and time to exhaustion was significantly less during trial CN than PL or GS, while PL and GS trials were similar. The data indicated that with 1 week of pretreatment there is no ergogenic effect of ingesting the ginseng saponin extract.
Asunto(s)
Ejercicio Físico/fisiología , Panax , Plantas Medicinales , Adulto , Glucemia/metabolismo , Ácidos Grasos no Esterificados/sangre , Femenino , Humanos , Cinética , Ácido Láctico/sangre , Masculino , Consumo de Oxígeno , RespiraciónRESUMEN
We examined the kinetics of phosphate transport in mouse renal brush-border membrane vesicles under initial rate (6 s), trans zero, voltage clamp conditions. Two kinetically distinct Na+-dependent phosphate transport processes were identified: a high-affinity, low-capacity system (Km, 0.09 +/- 0.02 mM; Vmax, 539 +/- 50 pmol/mg protein per 6 s) and a low-affinity, high-capacity system (Km, 1.28 +/- 0.35 mM; Vmax, 1677 +/- 198 pmol/mg protein per 6 s). The high-affinity system was inhibited competitively by 1 mM phosphonoformic acid (PFA) (apparent Ki, 0.31 +/- 0.03 mM) and completely abolished by 20 mM PFA; the low-affinity system was insensitive to 1 mM PFA and was inhibited competitively by 20 mM PFA (apparent Ki, 9.03 +/- 1.21 mM). Dietary phosphate deprivation elicited a significant increase in Vmax of both high- and low-affinity phosphate transport systems whereas the X-linked Hyp mutation caused a 50% decrease in Vmax of the high-affinity system with no change in the low-affinity system. Phosphate deprivation of Hyp mice elicited a 3.5-fold increase in Vmax of the high-affinity system. Neither diet nor mutation significantly altered the apparent Km values of either phosphate transport process. We conclude that (1) mouse kidney brush-border membranes have two distinct Na+-dependent phosphate transport systems which differ in affinity and capacity; (2) both processes participate in the adaptive response to dietary phosphate restriction; (3) only the high-affinity system is impaired by the X-linked Hyp mutation.
Asunto(s)
Riñón/metabolismo , Microvellosidades/metabolismo , Mutación , Compuestos Organofosforados/farmacología , Fosfatos/metabolismo , Ácido Fosfonoacético/farmacología , Animales , Transporte Biológico , Dieta , Femenino , Foscarnet , Cinética , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Mutantes , Fosfatos/farmacología , Ácido Fosfonoacético/análogos & derivadosRESUMEN
The X-linked hypophosphatemic (Hyp) mouse is a model for human X-linked hypophosphatemia. Surgical joining of normal to Hyp mice by parabiosis results in the normal mice developing low renal retention of phosphate and hypophosphatemia. These results suggest a humoral component to the renal defect. To test whether this component could be parathyroid hormone, surgical parathyroidectomy (PTX) or sham surgery was performed in mice 3 weeks after parabiotic union (n greater than 20 per group). After an overnight fast, PTX mice were hypocalcemic and hyperphosphatemic relative to sham-operated control mice. PTX normal mice joined to PTX Hyp mice were significantly lower in plasma phosphate and higher in fractional excretion of phosphate [U/P phosphate/(U/P creatinine)] when compared with PTX normal mice joined to other PTX normals. To test for more specific evidence of altered renal transport function, renal brush-border membrane vesicles (BBMV) were prepared from these mice, and phosphate and glucose uptakes were measured. The phosphate/glucose transport ratio was lower in BBMV from Hyp mice, joined to either normal mice or to Hyp mice, when compared with that from normal-normal pairs. Moreover, BBMV from normal mice joined to Hyp mice had a significantly lower phosphate/glucose uptake ratio than BBMV from normal mice joined to other normal mice, and their activity approached that of BBMV derived from Hyp mice. Glucose uptake in BBMV was unaffected by parabiosis or genotype. In summary, parabiosis of normal mice to Hyp mice resulted in the development of phosphaturia and decreased BBMV phosphate transport in the normal mice. The persistence of the phosphate transport defect in parathyroidectomized mice suggests that parathyroid hormone is not the humoral factor contributing to these results.
Asunto(s)
Hipofosfatemia Familiar/metabolismo , Riñón/metabolismo , Parabiosis , Hormona Paratiroidea/fisiología , Fosfatos/metabolismo , Fosfatasa Alcalina/metabolismo , Animales , Transporte Biológico , Calcio/sangre , Membrana Celular/metabolismo , Creatinina/sangre , Creatinina/orina , Femenino , Ligamiento Genético , Glucosa/metabolismo , Hipofosfatemia Familiar/genética , Masculino , Ratones , Microvellosidades/metabolismo , Glándulas Paratiroides/cirugía , Fenotipo , Cromosoma XRESUMEN
Two isozymes of enolase, alpha alpha and gamma gamma, have been purified from rabbit brain and characterized. The kinetic properties of alpha alpha and gamma gamma (pH optimum, Km for phosphoglycerate and phosphoenolpyruvate, requirement for a divalent cation) are very similar to those of rabbit enolase, form beta beta, and to those of enolase isozymes from other species. However, several novel properties were observed. (i) All the enolases studied were inhibited by Na+ and Li+. (ii) The rabbit enolases, but not yeast enolase, were activated by K+, NH4+, Cs+, and Rb+. (iii) Rabbit enolase is more susceptible to inhibition by excess Mg2+ than is the yeast enolase; the increased inhibition by Mg2+ above pH 7.1 accounts, at least in part, for the observed differences between mammalian and yeast enolases in their pH optima for activity.
Asunto(s)
Encéfalo/enzimología , Mamíferos/metabolismo , Fosfopiruvato Hidratasa/análisis , Saccharomyces cerevisiae/enzimología , Animales , Cationes Monovalentes , Cinética , Magnesio/farmacología , Peso Molecular , Fosfopiruvato Hidratasa/aislamiento & purificación , ConejosRESUMEN
The present study was undertaken to examine 1) the effect of phosphate restriction on growth hormone (GH) secretory dynamics in freely moving, chronically cannulated rats and 2) the effect of hypophysectomy on the renal adaptive responses to phosphate deprivation. Phosphate restriction led to an increase in renal brush-border membrane Na+-dependent phosphate transport (2,511 +/- 283 vs. 1,006 +/- 122 pmol.mg protein-1.15 s-1, P less than 0.001) and in the plasma concentration of 1 alpha,25-dihydroxyvitamin D [1,25(OH)2D] (127 +/- 10 vs. 63 +/- 4 pg/ml, P less than 0.001). In contrast, phosphate deprivation had no effect on either amplitude or frequency of spontaneous GH secretory bursts and did not alter pituitary GH concentration. Hypophysectomy led to a decrease in brush-border membrane Na+-dependent phosphate transport (669 +/- 78 vs. 1,006 +/- 122 pmol.mg protein-1. 15 s-1, P less than 0.003) and to a fall in plasma 1,25(OH)2D (42 +/- 9 vs. 63 +/- 4 pg/ml, P less than 0.02). Phosphate restriction of hypophysectomized rats elicited a twofold increase in Na+-dependent phosphate transport (1,312 +/- 106 vs. 669 +/- 78 pmol.mg protein-1.15 s-1, P less than 0.001) but no rise in plasma 1,25(OH)2D. We conclude that the renal adaptive responses to phosphate deprivation are not mediated by specific alterations in pulsatile GH secretion. Moreover, we demonstrate that the adaptive increase in brush-border membrane phosphate transport occurs after hypophysectomy, is not dependent on increased vitamin D hormone production, and is most likely subject to a different regulatory mechanism.
Asunto(s)
Aclimatación , Hormona del Crecimiento/metabolismo , Hipofisectomía , Riñón/metabolismo , Fosfatos/deficiencia , Hipófisis/fisiología , Animales , Calcitriol/sangre , Calcio/sangre , Calcio/orina , Creatinina/sangre , Glucosa/metabolismo , Hormona del Crecimiento/sangre , Riñón/efectos de los fármacos , Masculino , Microvellosidades/metabolismo , Fosfatos/sangre , Fosfatos/farmacología , Ratas , Ratas Endogámicas , Valores de ReferenciaRESUMEN
Vesicles enriched in the anion transport protein band 3 and its transmembrane domain were prepared, and the cysteine residues were labelled with an extrinsic fluorescent probe, monobromobimane. Fluorescence energy transfer was demonstrated between intrinsic tryptophans and monobromobimane, and an average interchromophoric distance, Rav, was defined. Rav values and fluorescence emission wavelengths were used to monitor the conformation of band 3 and its transmembrane domain as a function of cholesterol content. The vesicles were treated with ovolecithin liposomes to reduce the cholesterol concentration, and there was an increase in Rav from 17.25 to 20.70 A (1 A = 0.1 nm) in intact band 3. A somewhat smaller increase in Rav for the transmembrane domain was observed (18.03-19.04). The tryptophan fluorescence emission wavelength was also blue shifted in the cholesterol-depleted preparations relative to the untreated samples. Combining the effects of cholesterol depletion upon Rav and the fluorescence emission maxima, it is suggested that the conformation of band 3 is influenced by the level of cholesterol in the bilayer.
Asunto(s)
Proteína 1 de Intercambio de Anión de Eritrocito/metabolismo , Colesterol/farmacología , Transferencia de Energía , Humanos , Matemática , Conformación Proteica , Dodecil Sulfato de Sodio/farmacología , Espectrometría de FluorescenciaRESUMEN
Alkaline phosphatase activity in extracts of testes of sexually immature (13 days old) and sexually mature rats has been characterized by its heat sensitivity, the extent of inhibition by homoarginine and phenylalanine, and by polyacrylamide gel electrophoresis. The testicular enzyme appears to be a liver-bone-kidney-type alkaline phosphatase. There are no significant differences in the properties of the enzyme from animals of these two ages. Spermatocytes and early spermatids contain very little alkaline phosphatase activity; the specific activity of a nonflagellate germinal cell suspension is only 1/20th that of the whole testis. Since the constant level of activity in immature and mature animals is not consistent with the enzyme activity being present only in late spermatids, we conclude that the majority of the testicular enzyme is present in nongerminal cells. The presence of alkaline phosphatase in plasma membrane purified from testes of adult rats was demonstrated.
Asunto(s)
Fosfatasa Alcalina/análisis , Testículo/enzimología , Animales , Membrana Celular/enzimología , Electroforesis en Gel de Poliacrilamida , L-Lactato Deshidrogenasa/análisis , Masculino , Nucleotidasas/análisis , Ratas , Células de Sertoli/enzimología , Espermatogénesis , Testículo/citologíaRESUMEN
The subcellular localization of sulfogalactoglycerolipid in rat testicular germinal cells was determined. The sulfolipid of young rats was labelled in vivo with Na235SO4. Rat testis cell suspensions were prepared, homogenized, and centrifuged on linear, continuous, sucrose gradients. The labelled lipid had the identical equilibrium density distribution pattern as alkaline phosphatase, an enzyme of the plasma membrane. The pattern of the sulfolipid was different from the patterns of enzyme markers for the Golgi apparatus, lysosomes, mitochondria, and endoplasmic reticulum. From these results, we conclude that sulfogalactoglycerolipid is located on the plasma membrane of rat testicular germinal cells.