The effect of chromate on citrinin-induced renal dysfunction in the rat.

Previous studies in this laboratory revealed an effect of chromate to potentiate the nephrotoxic effects of mercuric ion. Citrinin, an organic anion, is a known nephrotoxin. The present study was undertaken to assess the possible interaction of chromate and citrinin on renal function. Male Sprague-Dawley rats were housed in metabolism cages and injected with citrinin (35 mg/kg), chromate (10 mg/kg) or the combination. The combination of nephrotoxicants caused an increased excretion of urine greater than the sum of the individual responses. A similar response was observed with urinary glucose concentrations and glucose excretion without changes in blood glucose levels. These data indicate that chromate can potentiate the nephrotoxic action of citrinin in the rat.

The effect of depletion of nonprotein sulfhydryls by diethyl maleate plus buthionine sulfoximine on renal uptake of mercury in the rat.

Rats pretreated with diethyl maleate (DEM, 3.37 mmol/kg, ip) and buthionine sulfoximine (BSO, 0.45 mmol/kg, ip) and subsequently given mercuric chloride (HgCl2, 0.014 mmol/kg, sc) had a significantly greater mortality rate over the 24 hr after injection than rats given only HgCl2 or HgCl2 following either DEM or BSO alone. Depletion of nonprotein sulfhydryls (NPSH) in the kidney significantly decreased mercury uptake in that organ. A similar effect was not seen in the liver despite marked depletion of NPSH. Similarly, there was a tendency for less in vitro mercury accumulation in renal cortical slices from rats made glutathione deficient by DEM + BSO compared to control, or rats made glutathione deficient by DEM or BSO alone. Depletion of nonprotein sulfhydryls by the combination of the depleting agents diethyl maleate plus buthionine sulfoximine (DEM + BSO) had a greater effect to alter organic ion accumulation in renal cortical slices than the agents alone. The higher mortality produced by mercuric chloride after DEM + BSO pretreatment may have been due to an increased availability of mercury in lethal concentrations at other organ sites. These data suggest the possible importance of NPSH in renal mercuric ion accumulation, but not in the liver.

Renal function in the rat after treatment with mercuric chloride plus potassium dichromate.

The treatment of rats with single subcutaneous (sc) doses of mercuric chloride (4 mg/kg) plus potassium dichromate (10 mg/kg) resulted in greater effects on water consumption, urine volume, body weight, and urinary electrolyte excretion than produced by mercuric chloride alone. The dose of potassium dichromate alone had no effects on renal function. Urine volume at 6 hr was increased twofold over mercuric chloride alone. Similarly, potassium excretion by these animals at 6 hr was significantly decreased compared to controls. These animals were oliguric by 24 hr after the injection. Urine osmolality of rats receiving the combination of the metals remained lower than controls throughout the 4-day experimental period. Measurement of renal arterial blood flow by electromagnetic flow probe after subcutaneous injection of saline, mercuric chloride (4 mg/kg), potassium dichromate (10 mg/kg), or the combination, produced no change over a 2.5-hr period, at 24 hr, and at 48 hr, and the glomerular filtration rate (GFR) of these rats was not affected over the same period of time.

The effect of potassium dichromate and mercuric chloride on urinary excretion and organ and subcellular distribution of [203Hg]mercuric chloride in rats.

The mechanism by which subthreshold/non-effective doses or concentrations of potassium dichromate (K2Cr2O7) potentiate the effect of moderately effective dose/concentrations of mercuric chloride (HgCl2) on renal organic ion transport is not understood. To investigate this effect, the rate of excretion of mercury from the intact animal and the renal and hepatic accumulation and subcellular distribution of mercury within kidney cortex following pretreatment or in vitro exposure to K2Cr2O7 were undertaken. Coincidental administration of K2Cr2O7 had no significant effect in altering the rate of excretion of labeled mercury. Organ distribution showed time dependence; however, the presence of K2Cr2O7 did not increase renal mercury concentrations. In fact, significantly less mercury was found at 4 h in the kidneys of rats receiving both metal salts. Subcellular distribution of labeled mercury (203Hg) was also not significantly altered by the presence of K2Cr2O7, although the distribution patterns for in vitro exposure and pretreated tissues were different. These studies show that K2Cr2O7 does not produce alterations in urinary elimination, organ distribution or subcellular distribution of mercury.

Renal glutathione and mercury uptake by kidney.

The kidney is well documented as the target organ for mercuric ion. Mechanisms by which this ion accumulates in renal tissue, however, are less well understood. Sulfhydryl groups in renal tissue might well bind this metal and serve as a sink for its accumulation. Various studies have indicated that both methyl mercury as well as mercuric ion are accumulated less by renal tissue after depletion of nonprotein sulfhydryl groups. A similar reduction in hepatic accumulation of mercuric ion or methyl mercury does not occur after nonprotein sulfhydryl depletion. This observation may relate to the higher tissue content of nonprotein sulfhydryls in liver than kidney or to a fundamentally different mechanism of metal uptake. Mercuric ion accumulation by renal tissue also can be reduced by ureteral occlusion, a reduction that is less than that for inulin in comparable experiments. These data are complex and do not clearly establish a role for filtration in the delivery of mercury to the kidney. Inhibition of the renal enzyme gamma-glutamyl transpeptidase (gamma-GT) results in a marked increase in the excretion of both glutathione and mercury in the urine. Although there is a tendency for kidneys of the gamma-GT-inhibited animals to contain less mercury than controls, the change in renal content was not significant. These observations suggest that gamma-GT may have a role in the reabsorption of mercury from the tubular lumen. Interestingly, both mercuric chloride-induced mortality and effects on renal slice accumulation of organic ions were enhanced in the presence of nonprotein sulfhydryl depletion caused both by immediate depletion of the glutathione pool and by inhibition of its synthesis.

Renal and hepatic glutathione concentrations in rats after treatment with hexachloro-1,3-butadiene and citrinin.

Renal and hepatic glutathione (GSH) concentrations were examined after treatment of male Sprague-Dawley rats with hexachloro-1,3-butadiene (HCBD) or citrinin alone and in combination, and after pretreatment with the GSH depleting agent diethylmaleate (DEM). It was found that both renal and hepatic GSH depletion were greater when either citrinin or HCBD was given following DEM. The effect was particularly striking when the doses used were so low as to be ineffective when given alone. When HCBD and citrinin were given in combination, the effect on GSH was approximately additive. Renal tubular organic ion transport in kidney slices was also compromised significantly when either citrinin or HCBD followed pretreatment with DEM. With HCBD, depression of tetraethylammonium (TEA) transport was seen after DEM; when given alone HCBD had no effect on TEA transport.

Interaction of potassium dichromate with the nephrotoxins, mercuric chloride and citrinin.

Potassium dichromate enhanced the effects of mercuric chloride or citrinin on renal slice transport of the organic ions p-aminohippurate (PAH) and tetraethylammonium (TEA) under certain experimental conditions. At the doses employed and times studied no effects, or only minimal effects, were observed on renal slice transport when the toxins were tested individually. Potassium dichromate (10 mg/kg) administered subcutaneously (s.c.) in combination with mercuric chloride (4 mg/kg, s.c.) or citrinin 35 or 55 mg/kg administered intraperitoneally (i.p.), resulted in a marked depression of organic ion transport. Similarly, the addition of potassium dichromate to fresh renal cortex slices in combination with mercuric chloride, enhanced the mercuric chloride-induced reduction of transport. No other interactions were observed under in vitro conditions.

Effects of fungal toxins on renal slice calcium balance.

Citrinin and ochratoxin A disrupt renal function in many animal species. The mechanism(s) underlying these actions is (are) unclear. Although citrinin has been shown to bind covalently to renal tissue, there also is evidence that it is active in the unmetabolized form. Altered calcium homeostasis has been suggested as an event which might mediate cell injury and/or death; a possible role for calcium in citrinin- or ochratoxin A-induced nephrotoxicity is reported here. Renal cortical slice calcium balance was monitored by the uptake of 45Ca. Either ochratoxin A or citrinin added to fresh renal cortex slices enhanced 45Ca accumulation. These effects were evident as early as 5 min after addition of the toxins. Greater 45Ca uptake occurred with bathing solution calcium concentration of 1.1 mM than in the absence of added carrier calcium. Finally, the effect of citrinin to reduce p-aminohippurate accumulation by renal cortical slices was greater in the presence of calcium than in its absence.

Idiopathic orthostatic hypotension: circulating noradrenaline and ultrastructure of saphenous vein.

The present study indicates that patients who can be clinically classified as idiopathic orthostatic hypotensives of the peripheral type are heterogeneous. There is the typical hypoadrenergic type characterized by low levels of circulating noradrenaline, much reduced or absent noradrenaline stores, and correspondingly little or no adrenergic innervation in the saphenous vein, a major capacitance vessel, as confirmed by ultrastructural examination. In one patient of this type, an abnormally high occurrence of mast cells in the blood vessel wall was noted. There also exists a category of individuals of the hyperadrenergic type, analogous to certain diabetics with noradrenergic abnormalities. These patients also are characterized by low levels of circulating noradrenaline, but noradrenaline stores are high; an exaggerated release of neurotransmitter occurs in response to stimuli; the saphenous vein with noradrenergic innervation remains ultrastructurally normal; however, the effector cell response are greatly blunted. In one patient of this type, the smooth muscle cells of the saphenous vein contained excessively high glycogen deposits. Further, it should be anticipated that a variety of intermediate types can be found as exemplified by one patient with variable, low to normal levels of circulating noradrenaline, a sluggish response to release neurotransmitter upon postural challenge, and considerable innervation of saphenous vein but with the majority of axons and terminals undergoing active degeneration.

Dopamine beta-hydroxylase distribution in density gradients: physiological and artefactual implications.

Knowledge of the vesicular origin of circulating dopamine beta-hydroxylase (DbetaH) is indispensable for any attempts to explain the parallelism or lack of it between circulating enzyme and catecholamines as they may relate to physiological stress, forms of hypertension, neurological disorders, and the response to pharmacological agents. The present study represents an effort to evaluate and to place in proper perspective data based on the DbetaH activity found in the region of the light vesicle peak of noradrenaline (NA), which is used as a quantitative measure of a population of small terminal vesicles. Distributions of vesicles and subvesicular components are compared with DbetaH and NA in sucrose-D2O density gradients used to prepare relatively pure fractions of large dense cored vesicles (LDV) from bovine splenic nerve. Although NA in sedimentable particles of the light vesicle peak is likely to be a valid measure of a small vesicle population, the following is demonstrated: (1) A substantial fraction (25%-37%) of the total sedimentable DbetaH activity can be proven to distribute in the region of the light vesicle peak from a tissue with an insignificant small vesicle population. Based on studies of vesicles from sequential nerve segments, this enzyme activity probably corresponds to a population of "immature" LDV which are undergoing axoplasmic transport and have not synthesized their full complement of transmitter. (2) Physical lysis which depletes the matrix of LDV causes redistribution of DbetaH activity from the heavy vesicle peak into the region of the light vesicle peak. Analogously, DbetaH associated with exocytosed LDV and retrograde transport particles is also likely to contaminate the region of the light vesicle peak. (3) Based on available data, it can be calculated that each small dense cored vesicle could contain only 0.1-0.5 molecules of DbetaH and that a contamination of only 0.016% LDV can account for all of the DbetaH reported to occur in the light vesicle peak of normal rat vas deferens preparations.