Testosterone treatment of female rats increased the elimination rate to a value similar to that of male rats. We used plasma of the same animal as a blank to correct for the absorbance caused by plasma components other than PAH. Renal cells are sensitive to the effect of testosterone. This mixture was centrifuged at rpm for 8 min.
Clearance of PAH and inulin were measured to estimate renal plasma flow and glomerular filtration rate, respectively, in anesthetized intact male empty bars and female rats filled bars. The jugular vein, the femoral artery, and the trachea were catheterized with polyethylene tubing. Slices were dried overnight at 80 C. Dry weight of tissue pieces was recorded in a Mettler Mexico City, Mexico M-5 balance, and are expressed as dpm per mg dry weight. Renal hemodynamics in intact male and female rats. To examine the tubular component of PAH excretion, in the absence of confounding factors such as renal hemodynamics and hepatic metabolism or excretion of this compound, we studied the in vitro uptake of PAH by cortical slices obtained from orchiectomized or intact male rats.
A blood sample obtained at the beginning of the experiment was used as a blank and to determine the initial hematocrit count.
Radioactivity was measured in a liquid scintillation spectrophotometer Tri-Carb, Packard. Sixty-day-old Wistar rats were used. The second group would be formed by intact females, orchiectomized rats, and ovariectomized rats. At the end of treatment, PAH kinetic studies were performed in these animals. At the end of each period, one group of slices was retired from the incubation media and blotted.
The mixture was agitated and centrifuged for 3 min at rpm. The testosterone dose used in this experimental series is higher than that employed by Fedor et al. PAH kinetic studies were performed min after administration.
Among other effects, testosterone promotes protein synthesis in mice The effect of exogenous testosterone was assessed in intact adult female rats. Restoration of the rate of PAH elimination from plasma with testosterone in orchiectomized rats. Janne et al. The size of the experimental groups was determined with basis on the method for sample size estimation in infinite populations 12and each group was formed by 20 rats.
PTH, in addition to its role on calcium regulation, also shows some degree of stimulation of secretory mechanisms 2. Inulin and PAH were measured as ly described The kinetics of PAH elimination was ificantly faster in intact males than in female rats, whereas the distribution kinetics was similar in both groups Fig.
Time course of the disappearance of PAH from plasma. Similarly, creatinine clearance increased — min after intramuscular administration of testosterone to rats This dose is fold higher than the dose required to induce an androgen effect in rats To induce an acute reduction of the androgen effect, 20 day-old rats were subjected to orchiectomy 15 days before the PAH kinetic studies.
Sampling was performed as ly described. Female adult Wistar rats were ovariectomized, and kinetic studies were performed in these animals.
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This dose does not saturate the transport system 11 ; therefore, the kinetics can be adequately estimated. Blood was obtained by cardiac puncture, and 9 ml were mixed with 1 ml sodium citrate 3. Experiments in the castrated animals were performed 15 days after surgery. The degree of PAH binding to plasma proteins might be a ificant factor contributing to the differences observed in its kinetic behavior in male and female rats.
We considered it of interest to study whether ovariectomy might affect PAH kinetics.
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Important consequences for pharmacokinetics stem from these differences males eliminate drugs faster than femalesbut they have seldom been taken into consideration. The bladder was catheterized with a double polyethylene tube, allowing for air injection to expedite emptying. The action of testosterone in a higher maximal transport capacity for glucose and a faster renal blood flow in men than in women. There were no differences in inulin or PAH clearances between male and female rats Fig. These indicate that renal hemodynamics does not contribute to the differences observed in PAH kinetics between intact male and female rats.
Therefore, we decided to study whether the binding of PAH to these proteins might explain the differences observed between male and female rats in renal excretion of PAH. Sixty-day-old male and female rats were anesthetized with ether. Differences between species have been noticed. These findings suggest that PAH secretion was dependent on testosterone activity. However, the analyses of the initial uptake rates indicate that these transporting sites have the same affinity in both groups of animals.
In vitro PAH uptake by renal cortical slices from intact male rats was higher than that by slices from orchiectomized rats. Orchiectomized rats were used 15 days after surgery.
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Kinetic analyses of PAH uptake suggest that the difference was caused by a lower of transporting molecules in orchiectomized than in intact animals, whereas the transporting capacity for each carrier was similar in male and in orchiectomized rats. Ammonium sulfamate 0. Plasma samples in the bags were introduced into vials containing 10 ml of phosphate buffer solution pH 7.
After the surgical preparation, plasma separated from blood collected from other rats was injected 1. The experimental procedure followed in the kinetic analysis was the same as described above. To gain further insight into this issue, we studied in vitro and in vivo characteristics of the transport of p -aminohippurate PAHa suitable marker for this system, in male and female rats, under different hormonal conditions.
Uptake was ificantly higher in slices from intact male rats than in those from orchiectomized rats Fig. These suggest that the differences between intact males and orchiectomized rats are caused by a greater of transporting sites for PAH in the intact animals than in the orchiectomized ones. PAH has been extensively used as an indicator of the renal secretory pathway of organic anions, because it is not biotransformed and is secreted by the proximal tubule.
Harvey and Malvin 7 reported that male rats secrete creatinine, probably through the organic anion pathway, but female rats do not. An equivalent volume of isotonic saline solution was infused to restore the amount extracted in the samples. A final sample for hematocrit was obtained, once the sampling for kinetics was completed.
At this age, sexual maturation has already been achieved The trachea was isolated, and a catheter was inserted to allow adequate ventilation.
The disappearance of PAH from plasma was measured in intact empty barorchiectomized filled barand testosterone-treated orchiectomized male rats hatched bar. Thyroid hormones have stimulatory effects on the function of renal cells, e.
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Therefore, the main effect of testosterone is to modulate the of functional transporting molecules in the cell membrane, without producing any evident changes in the transport speed of each of these carriers. Radioactivity was measured in a liquid scintillation counter Packard Tri Carb, modInstrumental Technion, Mexico City, Mexicoand corrections for quenching and background were made. Our suggest that testosterone increases the of functional carriers for PAH in the kidney. PAH uptake by renal cortical slices obtained from intact and orchiectomized male rats.
All experimental procedures were performed in accordance with international recommendations for the use and care of laboratory animals. This compound was chosen to estimate its disappearance rate from plasma in male and female rats and to look for differences possibly attributable to sexual dimorphism. Samples were kept in the dark for 20 min. Renal secretion of organic anions is higher in male than in female individuals; as a consequence, most of the xenobiotics that are excreted from the organism through this pathway are eliminated more rapidly by males than by female animals.
Cortical slices were obtained from intact male or orchiectomized rats.
Concentrations of PAH in plasma were measured using the method described by Bratton and Marshall 13modified for small samples. To prevent hemodynamic systemic factors from participating in the presumable differences between orchiectomized and intact male rats, we measured PAH uptake in cortical renal slices. The carotid artery and the jugular vein were both catheterized to obtain samples and to administrate test compounds, respectively. Some metabolic effects of testosterone may be mediated by the interaction of the hormone with estrogen receptors in the target cells.
Corrections for background and quenching were made. It was mandatory, therefore, to study this issue.
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In regard to sexual hormones, it has been suggested that testosterone has a stimulatory effect on several renal cellular functions, such as secretion 3whereas female sexual hormones do not show any clear effect on secretion 4. Louis, MOas ly described Pharmacokinetics is highly dependent on the degree of drug binding to plasma proteins. This is specially relevant to the use of drugs with a narrow therapeutic index and high potential toxicity. Testosterone increased chloride transepithelial transport and cAMP levels in an established cell line MDCK derived from canine distal nephron 5.