Cyclosporine-induced alterations in the hypothalamic hypophyseal gonadal axis in transplant patients.

We evaluated the response of 20 male patients, 13 cadaveric kidney and 7 heart transplant recipients, to the administration of 100 micrograms GnRH (gonadotropin-releasing hormone) and 500 micrograms TRH (thyrotropic-releasing hormone). All of the heart transplant recipients and 7 of the kidney transplant patients were receiving a combination of cyclosporine, azathioprine and prednisone; while the 6 remaining kidney transplant patients received azathioprine and prednisone. The patients receiving cyclosporine had decreased plasma levels of prolactin, and manifested a blunted response to TRH administration for prolactin and TSH. The heart transplant patients had a blunted response of LH and FSH to the administration of GnRH. The levels of testosterone were found to be low in all patients regardless of the immunosuppressant therapy. Despite the low testosterone levels, no increment in the concentration of LH or FSH was present. Intramuscular administration of HCG (human chorionic gonadotropin) (Ayerst Laboratories, New York, N.Y.) failed to increase the testosterone concentration in 5 of 6 patients with renal transplants, 3 taking cyclosporine and 3 taking azathioprine. This study suggests that cyclosporine has a selective effect on the hypothalamus and/or hypophysis, resulting in lower baseline levels of plasma prolactin and a pituitary insensitivity to TRH administration. In addition, FSH and LH were low or normal in the presence of low testosterone levels, suggesting that the hypothalamic pituitary gonadal axis is impaired. Furthermore, there may be a direct toxic effect of the immunosuppressant medications on the gonads, manifested as lower testosterone levels and inability to respond to the administration of HCG.

OKT3 prophylaxis versus conventional drug therapy: single-center perspective, part of a multicenter trial.

As part of a collaborative study, Orthoclone OKT3 (Ortho Pharmaceutical Corporation, Raritan, NJ) monoclonal anti-T-cell antibody was used prophylactically for 14 days following cadaveric renal transplantation. Patients were randomized before treatment and compared with a control group treated with triple-drug immunosuppressant therapy consisting of cyclosporine, azathioprine, and prednisone. The OKT3 group (also treated with prednisone and azathioprine) had significantly fewer patients with acute rejection during the first year (27% v 60%), significantly delayed onset of acute rejection (median number of days to rejection, 56 v 10), and shortened duration of delayed initial graft function (median number of days on nonfunction, 5.5 v 9.0). OKT3 was safely administered intraoperatively. The study group included diabetics and patients over the age of 50 years. There was an increased incidence of benign fungal infection in patients treated with OKT3. The outcome data of both the prophylactic and control groups in this single-center trial was different from the multicenter experience in that patient and graft survival was 100% in both groups. The only difference in the immunosuppressive protocol was the use of 2 g intravenous methylprednisolone intraoperatively. The combination of intraoperative OKT3 with 2 g methylprednisolone may merit further study. It was concluded that OKT3 prophylaxis reduces the incidence of rejection episodes, delays the occurrence of rejection, and may reduce the duration of delayed initial graft function. It is not associated with an increase in serious infection and can be administered safely to a variety of cadaver transplant recipients.

Occupational exposure to organic solvents causing chronic tubulointerstitial nephritis.

We describe a patient with a history of ulcerative colitis and long-standing occupational exposure to organic solvents. Over a follow-up period of almost four years he had progression of tubulointerstitial damage documented by two kidney biopsies. We propose that long-term exposure to organic solvents can lead to the development of chronic tubulointerstitial nephritis. We describe experimental evidence that supports our conclusion.

Proteinuria in hypertension.

It had been previously thought that protein excretion in hypertensive nephrosclerosis was less than 0.5 to 1.0 g/24 h. Furthermore, it was believed that proteinuria in the nephrotic range associated with hypertension was probably due to primary renal disease, malignant hypertension, renal artery stenosis, or pheochromocytoma. We report eight patients with biopsy-proven hypertensive nephropathy and heavy proteinuria in the absence of malignant hypertension or renal artery stenosis. The 24-hour protein excretion ranged from 2.7 to 4.3 g. All patients had renal insufficiency, with serum creatinine ranging from 2.0 (176.8) to 7.8 mg/dL (689.5 mumol/L). Renal function worsened in most patients during the follow-up period despite adequate control of the hypertension, and three patients had to be started on hemodialysis. Three patients died during the follow-up period. We conclude that hypertensive nephrosclerosis must be included in the differential diagnosis of marked proteinuria in patients with essential hypertension and that heavy proteinuria, along with renal insufficiency, are poor prognostic indicators in such patients.

Effects of intracellular sodium and potassium iontophoresis on membrane potentials and resistances in toad urinary bladder.

Glass microelectrodes were used to measure membrane potentials and the ratio of apical to basolateral membrane resistances before and after the passage of current from the potential-recording microelectrode to ground, in toad urinary bladder epithelium, in order to iontophorese cations into the cell. After application of the current, there was a transient change in the tip potential of the microelectrode. This artifact was measured with the microelectrode in the mucosal medium and was subtracted from the potential recorded in the cell. The serosal medium was bathed by Ringer's solution containing 51.5 mM K+ to minimize any current-induced increase of K+ in the unstirred layer. Under those conditions, both Na+ and K+ iontophoresis caused a significant hyperpolarization of basolateral membrane potential (Vcs) and a significant increase in the ratio of apical to basolateral membrane resistances (Ra/Rb). When bladders were exposed to amiloride in the mucosal solution, Na+ iontophoresis caused the basolateral membrane to hyperpolarize, but no significant changes were observed in Ra/Rb. When Na+ was injected in the presence of serosal ouabain, Vcs depolarized and Ra/Rb increased. K+ iontophoresis caused the basolateral membrane potential to hyperpolarize in the presence of ouabain but Ra/Rb did not change significantly. These results indicate that the Na+ pump in toad bladder is rheogenic, that apical Na+ conductance is sensitive to the cell levels of Na+ and K+ and that the basolateral membrane is K+ permeable.

Effects of changes in serosal chloride on electrical properties of toad urinary bladder.

Conventional microelectrode and tracer flux techniques were used to study the effects of reduction in serosal chloride concentration ([Cl]s) on the electrical properties of toad urinary bladder epithelium. Reduction in [Cl]s resulted in a transient change in transepithelial potential (Vms) (and of apical and basolateral membrane potentials) that was inversely dependent on the base-line values of those potentials. In all cases, however, there was a decrease in transepithelial resistance (Rt) that was explained by an increase in the sodium conductance of the apical membrane. In tissues in which the transepithelial potential increased, there was a rise in the active mucosal-to-serosal sodium flux. The increase in conductance was directly related to the increase in short-circuit current. The changes in Vms and Rt brought about by reduction in [Cl]s were prevented by agents known to modify sodium transport, including low mucosal sodium concentration, addition of amiloride or amphotericin B to the mucosal solution, or of ouabain to the serosal solution. The results are best explained by a primary effect of chloride reduction on sodium extrusion across the basolateral membrane, with a secondary increase in apical sodium conductance. In addition, the data provide new evidence for the existence of a basolateral chloride conductance pathway.

Anion-sensitive sodium conductance in the apical membrane of toad urinary bladder.

Membrane potentials and the electrical resistance of the cell membranes and the shunt pathway of toad urinary bladder epithelium were measured using microelectrode techniques. These measurements were used to compute the equivalent electromotive forces (EMF) at both cell borders before and after reductions in mucosal Cl- concentration ([Cl]m). The effects of reduction in [Cl]m depended on the anionic substitute. Gluconate or sulfate substitutions increased transepithelial resistance, depolarized membrane potentials and EMF at both cell borders, and decreased cell conductance. Iodide substitutions had opposite effects. Gluconate or sulfate substitutions decreased apical Na conductance, where iodide replacements increased it. When gluconate or sulfate substitutions were brought about the presence of amiloride in the mucosal solution, apical membrane potential and EMF hyperpolarized with no significant changes in basolateral membrane potential or EMF. It is concluded that: (a) apical Na conductance depends, in part, on the anionic composition of the mucosal solution, (b) there is a Cl- conductance in the apical membrane, and (c) the electrical communication between apical and basolateral membranes previously described is mediated by changes in the size of the cell Na pool, most likely by a change in sodium activity.

Microelectrode studies in toad urinary bladder epithelium. effects of Na concentration changes in the mucosal solution on equivalent electromotive forces.

Microelectrode techniques were employed to measure membrane potentials, the electrical resistance of the cell membranes, and the shunt pathway, and to compute the equivalent electromotive forces (EMF) at both cell borders in toad urinary bladder epithelium before and after reductions in mucosal sodium concentration. Basal electrical parameters were not significantly different from those obtained with impalements from the serosal side, indicating that mucosal impalements do not produce significant leaks in the apical membrane. A decrease in mucosal Na concentration caused the cellular resistance to increase and both apical and basolateral EMF to depolarize. When Na was reduced from 112 to 2.4 mM in bladders with spontaneously different baseline values of transepithelial potential difference (Vms), a direct relationship was found between the change in Vms brought about by the Na reduction and the base-line Vms before the change. A direct relationship was also found by plotting the change in EMF at the apical or basolateral border caused by a mucosal Na reduction with the corresponding base-line EMF before the change. These results indicate that resting apical membrane EMF (and, therefore, resting apical membrane potential) is determined by the Na selectivity of the apical membrane, whereas basolateral EMF is at least in part the result of rheogenic Na transport. These results are consistent with data of others that suggested a link between the activity of the basolateral Na pump and apical Na conductance.

Effect of harmaline on pacemaker activity of guinea pig sinus node.

Transmembrane potentials of pacemaker fibers of the sinus node were recorded to analyze the effect of harmaline (HME) on cardiac automaticity. A short exposure to HME 2.1 X 10(-5) or 8.3 X 10(-5) M produced a long lasting non-cholinergic depression of the automaticity: the slope of diastolic depolarization of the pacemaker fibers was depressed, but the maximum diastolic potential remained unmodified. The automaticity of the sinus node was not abolished by prolonged exposure to HME 8.3 X 10(-4) M, but a reversible sino-atrial block developed.

Catechol-mediated effects of harmaline on the action potential of rat atrial fibres.

The mechanism of the transient enhancement of the amplitude of the action potential (AAP) induced by harmaline (HME) was studied in rat atria. The results show that HME increases AAP through an enhancement of the slow component responsible for the last part of the upstroke, which overcomes an inhibitory action on the initial fast component. The stimulatory effect on the slow component is mediated through adrenergic beta receptors and normally masks an alpha-dependent depressant effect.

The effect of harmaline on membrane potentials of rat atrial contractile fibers.

Rat atria either beating spontaneously or electrically driven were were perfused in vitro at 30 degrees C. When the preparations were exposed to harmaline 8.3 x 10(-5) or 16.6 x 10(-5) M the atrial rate showed down and the following changes in membrane potentials were observed: (1) a transient increase in the amplitude of the action potential (AAP), in the absence of any change in the magnitude of the resting potential (RP), followed by a progressive decrease of AaP; (2) a progressive decline of the slope of the fast ascending phase of the action potential, which was initially independent of any change in the magnitude of the rp; (3) a progressive increase of the duration of the action potential; (4) a fall in the magnitude of the resting potential. The conclusions proposed are that harmaline: (1) stimulates the slow current responsible for the last part of the upstroke and the beginning of the repolarization; (2) inhibits the sodium current responsible for the fast component of the upstroke; (3) slows doen the processes responsible for the repolarization; (4) inhibits the (Na+-K+) activated membrane ATPase.

The effect of harmaline on force of contraction of the rat isolated atrium.

In rat isolated right atria, beating spontaneously at 30 degrees C, harmaline 8.3 times 10-5 M slowed atrial rate and enhanced force of contraction. The velocity of development of tension (dT/dt) increased and time to peak tension was lengthened. Electrical drive of otherwise quiescent left atria showed that (1) within the range of change of rate induced by harmaline the reduction of frequency of stimulation increased dT/dt and peak tension developed, and (2) at a constant rate of stimulation harmaline produced a prolongation of time to peak tension and an enhancement of peak tension. We concluded that two mechanisms are responsible for the inotropic action of harmaline on rat atrium: (1) an increase in dT/dt due to the lengthening of the interval between beats; (2) a direct action of harmaline on the processes responsible for atrial contraction, which determines a lengthening of time to peak tension.