Production and metabolic clearance of calcitriol in acute renal failure

Metabolic clearance rate (MCR) and production rate (PR) of calcitriol were studied three and seven days after ischemic acute tubular necrosis (ATN). Creatinine clearance was decreased three days after clamping the renal arteries (0.42 +/- 0.03 ml/min/100 g, N = 6 in ATN vs. 0.68 +/- 0.09, N = 7 in sham controls; P less than 0.001). Plasma concentrations (24.1 +/- 1.9 pg/ml) and PR of calcitriol (9.8 +/- 0.91 ng/kg/day) were significantly lower in ATN rats three days after ischemic insult when compared to sham control rats, respectively (76.6 +/- 7.3 pg/ml, and 29.6 +/- 3.3 ng/kg/day; both P less than 0.01). The MCRs of calcitriol were not different between ATN (0.28 +/- 0.02 ml/min/kg) and sham control rats (0.27 +/- 0.01). By the seventh day after ischemic injury, when creatinine clearance of ATN rats returned to normal, both the PR and plasma concentrations of calcitriol also returned to normal values in these animals. In order to assess the effect of uremia on calcitriol metabolism, MCR and PR of calcitriol were measured in rats with reinfusion of their urines for 24 hours. The PR of calcitriol was significantly decreased (9.42 +/- 1.21; vs. controls, 20.5 +/- 2.9 ng/kg/day, P less than 0.001) in uremic animals. Since decreased PR of calcitriol was also accompanied by decreased MCR of calcitriol, plasma concentrations of calcitriol of the uremic rats with intact kidneys remained within normal values. We conclude that the PR of calcitriol is decreased early in ATN rats. Although the MCR was not decreased in mild ATN rats, it may decrease in severe acute renal failure.

Calcemic response to parathyroid hormone in spontaneously hypertensive rats: role of calcitriol

Spontaneously hypertensive rats (SHR) display lower ionized calcium (Pca++) concentrations when compared with normotensive Wistar Kyoto rats (WKY). This could be attributable to renal wasting of calcium, decreased intestinal calcium absorption, or decreased bone resorption, processes that are integrated by the parathyroid hormone (PTH) and vitamin D systems. We have studied the calcemic response to PTH infusion (3 U/hr/100 gm) for 5 hours in 13-week-old SHR and WKY. Pre-PTH Pca++ concentration of nonfasted SHR (4.68 +/- 0.06 mg/dl, N = 8) was significantly lower than that of WKY (4.84 +/- 0.03, N = 8, P less than 0.05). Pca++ concentration rose in both nonfasted WKY and SHR at the end of PTH infusion, but the increment of Pca++ in SHR (0.29 +/- 0.05 mg/dl, N = 8) was lower than that in WKY (Pca++, 0.60 +/- 0.07 mg/dl, N = 8, P less than 0.01). Urinary calcium excretion (UcaV) and creatinine clearances (Ccr) before and after PTH infusion were not different between WKY and SHR. Despite an increased filtered load of calcium, UcaV was not greater in either WKY or SHR during the PTH infusion. Pretreatment of SHR with calcitriol 50 ng intravenous bolus injection, which had no effect on Pca++ concentration (0.02 +/- 0.03 mg/dl, N = 7), corrected the lower calcemic response to PTH in SHR, and the Pca++ increment was no longer different between WKY (0.57 +/- 0.07 mg/dl, N = 7) and SHR (0.62 +/- 0.09, N = 7).(ABSTRACT TRUNCATED AT 250 WORDS)

Production and degradation of calcitriol in renal failure rats

We studied the metabolism of calcitriol in renal failure achieved by nephrectomy in three groups of rats. Group 1 (n = 7) had sham operation of nephrectomy. Group 2 (n = 8) had unilateral nephrectomy. Group 3 (n = 7) had 5/6 nephrectomy. Metabolic clearance rate (MCR) and production rate (PR) of calcitriol were studied 3 wk after the surgery. Serum creatinine concentrations were increased after nephrectomy for groups 2 and 3. Endogenous plasma levels of calcitriol were not different between the rats with renal failure and the controls. MCR of calcitriol were decreased in renal failure rats compared with controls (group 1, 0.24 +/- 0.01; group 2, 0.20 +/- 0.01, P less than 0.01; group 3, 0.16 +/- 0.01 ml.min-1.kg-1, P less than 0.001). The MCR of calcitriol was correlated with the endogenous creatinine clearance by linear regression analysis (r = 0.72, P less than 0.001). The PR of calcitriol were also decreased in renal failure; however, the decreases were much less than the amount of renal tissue removed. We concluded that production of calcitriol is decreased in the remnant kidney. The decreased synthesis is associated with decreased degradation of calcitriol resulting in normal concentrations of calcitriol in mild to moderately severe renal failure.

Calcium and vitamin D metabolism in spontaneously hypertensive rats

We have studied the effect of dietary vitamin D restriction on serum levels of vitamin D metabolites in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). Both WKY and SHR were fed a vitamin D-deficient or a vitamin D-supplemented diet beginning at 4 wk of age. In vitamin D-supplemented animals, the serum 1,25-dihydroxycholecalciferol [1,25(OH)2D3] concentration of WKY (55.4 +/- 6.6 pg/ml, n = 5) was similar to the level of SHR (46.3 +/- 5.9 pg/ml, n = 5). Plasma calcium concentration was not different between WKY and SHR. In animals fed a vitamin D-deficient diet, the serum concentration of 1,25-(OH)2D3 of SHR (23.0 +/- 1.3 pg/ml, n = 5) was significantly lower than that of WKY (67.6 +/- 4.6 pg/ml, n = 5, P less than 0.01). Plasma 25-hydroxycholecalciferol level was markedly decreased in both WKY (3.6 +/- 0.5 ng/ml, n = 7) and SHR (2.8 +/- 0.4 ng/ml). The SHR, but not the WKY, developed hypocalcemia (WKY, 9.68 mg/dl; SHR, 6.70 mg/dl). Despite hypocalcemia, fasting urinary Ca2+ excretion of SHR exceeded that of WKY. We conclude that the lower 1,25(OH)2D3 level in SHR fed a vitamin D-deficient diet may be due to a defect in the synthesis of 1,25(OH)2D3. The low level of 1,25(OH)2D3 is associated with renal wasting of calcium and hypocalcemia in SHR.

Alterations in renal structure and function in a rat model of cyclosporine nephrotoxicity

Adult male Sprague-Dawley rats maintained on a low sodium diet were administered 100 mg of cyclosporine per kg b.wt. per day s.c. for 4 to 10 days. Serum urea nitrogen was significantly elevated by day 4 and continued to rise, whereas serum creatinine was not elevated above control until day 10. Morphologic examination of perfusion-fixed kidneys from cyclosporine-treated rats revealed focal areas of tubular atrophy and interstitial fibrosis in the outer cortex and a generalized increase in interstitial cells in the outer medulla. No areas of acute tubular necrosis were identified. The effect of this dose of cyclosporine on renal hemodynamics was examined in conscious restrained rats. Renal blood flow, measured by microsphere injection, was 70% of control after four daily doses and remained near this level after eight daily doses. The glomerular filtration rate, measured by iodothalamate clearance, was 70% of control after four doses but fell to 34% of control after eight doses. [3H]Thymidine incorporation into renal DNA was used as a sensitive index of renal cell proliferation after cyclosporine administration (100 mg/kg/day). [3H]Thymidine incorporation was increased over control 3-fold in the outer cortex, 7-fold in the inner cortex and 11-fold in the medullary-papillary regions of the kidney after eight daily doses of cyclosporine. Histoautoradiographic examination of renal sections revealed an increase in the number of labeled nuclei in all three regions of the kidney from rats treated with cyclosporine. Morphometric analysis demonstrated that the majority of proliferating cells were located in the interstitium and not in renal tubules.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic degradation and synthesis of calcitriol in spontaneously hypertensive rat

Plasma calcitriol concentration is unexpectedly low in spontaneously hypertensive rats (SHR) compared with normotensive Wistar-Kyoto rats (WKY) in view of previous findings of low plasma ionized calcium, hypophosphatemia, and hyperparathyroidism in SHR. Also, parathyroid hormone (PTH) and other exogenous stimuli cause a smaller increment in plasma calcitriol in SHR than in WKY. We investigated whether these differences in plasma calcitriol levels were due to decreased production rate (PR) or increased metabolic clearance rate (MCR) in SHR using the continuous infusion-isotope equilibration technique. In the basal state, MCR was 0.306 +/- 0.048 ml X min-1 X kg-1 in SHR and 0.284 +/- 0.026 ml X min-1 X kg-1 in WKY (P = NS). Estimated PR was lower in SHR (22.7 vs. 33.7 ng X day-1 X kg-1). With PTH infusion (3 U X h-1 X 100 g-1 for 20 h), MCR was 0.220 +/- 0.011 ml X min-1 X kg-1 in SHR and 0.256 +/- 0.017 ml X min-1 X kg-1 in WKY (P = NS). Measured PR was markedly lower in SHR (154 +/- 24 vs. 262 +/- 27 ng X day-1 X kg-1; P less than 0.02). Basal plasma PTH, total plasma calcium, and plasma inorganic phosphate were not different between SHR and WKY. Thus, SHR show diminished calcitriol production under basal condition and with PTH stimulation. MCR is not increased in SHR and does not appear to be influenced by PTH or the accompanying elevation in plasma calcium and calcitriol.

Plasma 1,25(OH)2D3 response to parathyroid hormone, cyclic adenosine monophosphate, and phosphorus depletion in the spontaneously hypertensive rat

Spontaneously hypertensive rats (SHR) have several abnormalities of calcium metabolism compared with normotensive control Wistar-Kyoto (WKY) rats. Previously the vitamin D metabolite 1,25-dihydroxycholecalciferol (1,25[OH]2D3) was found to be inappropriately low in SHR in view of their ionized hypocalcemia and hyperparathyroidism. We examined the responses of plasma 1,25(OH)2D3 to several known stimuli. Baseline plasma 1,25(OH)2D3 levels tended to be lower in SHR than WKY rats (51.5 +/- 4.3 vs. 82.3 +/- 14.1 pg/ml, P = 0.06). Infusion of a pharmacologic dose of parathyroid hormone (8 U/hr over a period of 17 hours) resulted in a plasma 1,25(OH)2D3 level of 504 +/- 77 pg/ml in SHR vs. 1016 +/- 211 pg/ml in WKY rats (P less than 0.03). Cyclic adenosine monophosphate infusion (1 mumol/hr/100 gm over a period of 17 hours) in thyroparathyroidectomized animals resulted in a 1,25(OH)2D3 level of 121 +/- 24 pg/ml in SHR vs. 557 +/- 26 pg/ml in WKY rats (P less than 0.01). After dietary phosphorus depletion for 3 weeks, SHR also had lower 1,25(OH)2D3 levels than WKY rats (83 +/- 13 vs. 300 +/- 42 pg/ml, P less than 0.001) even though a comparable degree of hypophosphatemia was achieved. Thus, the response of plasma 1,25(OH)2D3 levels to several known stimuli is submaximal in SHR as compared with WKY rats, suggesting defective synthesis or enhanced metabolic clearance of this hormone.

Serial immunologic and histopathologic studies in the treatment of necrotizing fasciitis with combined immunodeficiency by a bovine thymic extract (thymostimulin)

A 25-day-old Chinese female baby developed necrotizing fasciitis (NF) with indurated erythematous patches with superficial necrosis over two thirds of the back. Skin cultures of the lesions yielded Streptococcus pyogenes, enterococcus, Pseudomonas aeruginosa, and Candida species. The patient had lymphopenia with low T cells and T cell subsets. The lymphoproliferative response to mitogen and macrophage migration (MIF) production were also poor. Her lymphocytes were unable to produce IgG in vitro. Also, IgG bearing cells were not demonstrable. The initial lymph node biopsy demonstrated an absence of follicular formation and depletion of lymphocytes in both thymic-dependent and thymic-independent areas. Five weeks after bovine thymic extract (Thymostimulin) treatment, a second lymph node biopsy demonstrated germinal centers containing IgG bearing cells. Three weeks later, a third lymph node biopsy showed germinal centers with cuffs of lymphocytes. Differentiation of the cortex and medulla of the node was demonstrated. IgG was also detectable in an in vitro Ig synthesis study. The total T cells, T cell subsets, lymphoproliferative response MIF production also increased gradually after Thymostimulin treatment. This investigation demonstrated the therapeutic effectiveness of Thymostimulin in NF with underlying combined immuno-deficiency, both serious and frequently fetal diseases, by the histologic and immunologic reconstitution of T and B cell function.

Sonographic finding of the bright thalamus

Six of 83 asphyxiated neonates showed a diffuse increase of echodensity in bilateral thalami with or without other lesions in the basal ganglia on sonographic examination. The thalamic image still had a fairly high echogenecity compared with the surrounding brain parenchyma on follow up examination and was hence termed the bright thalamus. These six patients had a poor neurological outcome, including psychomotor retardation, spastic diplegia or quadriplegia, microcephaly, failure to thrive, seizures, and one death. The bright thalamus is not an occasional or an isolated sonographic finding of hypoxic-ischaemic encephalopathy, but it may serve as a landmark of severe hypoxic brain damage with adverse outcome.

DNA and amino acid sequence analysis of structural and immunity genes of colicins Ia and Ib

The nucleotide sequences for colicin Ia and colicin Ib structural and immunity genes were determined. The two colicins each consist of 626 amino acid residues. Comparison of the two sequences along their lengths revealed that the two colicins are nearly identical in the N-terminal 426 amino acid residues. The C-terminal 220 amino acid residues of the colicins are only 60% identical, suggesting that this is the region most likely recognized by their cognate immunity proteins. The predicted proteins for the colicin immunity proteins would contain 111 amino acids for the colicin Ia immunity protein and 115 amino acids for the colicin Ib immunity protein. The colicin immunity proteins have no detectable DNA or amino acid homology but do exhibit a conservation of overall hydrophobicity. The colicin immunity genes lie distal to and in opposite orientation to the colicin structural genes. The colicin Ia immunity protein was purified to apparent homogeneity by a combination of isoelectric focusing and preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The N-terminal amino acid sequence of the purified Ia immunity protein was determined and was found to be in perfect agreement with that predicted from the DNA sequence of its structural gene. The Ia immunity protein is not a processed membrane protein.

Social isolation inhibits male-like sexual behavior in female hamsters

In the female golden hamster, Mesocricetus auratus, group housing permits the expression of male-like behavioral patterns including mounting and pelvic thrusting toward an estrous stimulus female. Sixty percent of females housed in groups of five showed these behaviors, while singly housed females were rarely observed to show mounting or thrusting. Females weaned at 19 or 35 days of age did not differ in their tendencies to show male-like behavioral patterns. Virtually all observations of mounting and pelvic thrusting behaviors were made on days when the females being tested were in behavioral estrus. These findings differ from previous studies which have reported that masculine behavioral patterns are rare in normal female hamsters. In previous studies females that were evaluated were typically not in behavioral estrus and were not housed for long periods of time with other intact females. Social factors interact with hormonal state to contribute to the expression of male-like behaviors in female hamsters.

Effects of furosemide diuresis on mercuric chloride-induced acute renal failure in the rat

In previous studies in rats given mercuric chloride (HgCl2), administration of furosemide has been found to either attenuate, exacerbate, or not affect the severity of the acute renal failure (ARF) otherwise expected to obtain. In the current study in rats given large doses of furosemide and in which urinary fluid losses were replaced by intravenous infusions of saline, administration of HgCl2 induced less severe ARF than that induced in rats not given furosemide and saline infusions. In rats not given furosemide, a diuresis induced by continuous reinfusion of urine also conferred protection against the nephrotoxic effect of HgCl2. These findings suggest that in rats given HgCl2: diuresis per se is the critical determinant of any salutary effect of furosemide and the protective effect of diuresis does not depend on renal elimination of mercury.