[Complications in the use of mechanical ventilator in newborns: one year's experience]

A retrospective study was undertaken of 175 patients (119 males, 56 females) admitted to the neonatal intensive care unit of Mackay Memorial Hospital during the period of July 1, 1985 to June 30, 1986 who received mechanical ventilation during their stay at the hospital. Upon reviewing the clinical histories of these patients, the complication rate of mechanical ventilation was 31.9%. The percentages of each complication were: pneumothorax 50.0%, pneumomediastinum 5.2%, pulmonary interstitial emphysema 1.7%, atelectasia 13.8%, pneumonia 13.8%, chronic lung disease 13.8%, nasopharyngeal infection 1.7%. Survival rate of these ventilated patients with or without complication was not significant statistically (69.2% vs 65.6%). However, with regard to the hospital course, cases with complication had a significantly longer duration of ventilator usage, hospital stay and oxygen usage than uncomplicated cases. In conclusion, experienced personnel are needed to supervise the use of mechanical ventilation in neonates, and a team of well-trained nurses working in the neonatal intensive care unit are essential to minimize complications.

Effects of purine derivatives on calcitriol metabolism in rats

The effects of theophylline and sodium urate on metabolic production (PR) and clearance rate (MCR) of calcitriol were determined by the constant isotope infusion method in normal rats. Calcitriol PR was significantly reduced after infusion for 20 h of either theophylline (1 mg/h, PR = 22.3 +/- 1.6 ng.kg-1.day-1, P less than 0.001, n = 5) or sodium urate (0.5 mg/h, PR = 18.6 +/- 1.2 ng.kg-1.day-1, P less than 0.001, n = 5) compared with control rats infused with saline (PR = 32.0 +/- 1.5 ng.kg-1.day-1, n = 5). Renal 1 alpha-hydroxylase activity of kidney homogenate was significantly inhibited in rats infused with theophylline or urate. Suppression of 1 alpha-hydroxylase activity was also observed when the kidney homogenate was preincubated for 3 h with various concentrations of xanthine (0.11-3.0 mg/dl). In addition, the MCR of calcitriol was decreased in rats infused with either theophylline (MCR = 21.0 +/- 0.88 microliter.min-1.100 g-1, P less than 0.005) or urate (MCR = 22.9 +/- 0.91 microliter.min-1.100 g-1, P less than 0.05) compared with saline-infused control rats (MCR = 25.2 +/- 0.41 microliter.min-1.100 g-1). Because calcitriol degradation is a receptor-mediated process that requires binding of the receptor-hormone complex to chromatin, we studied the binding affinity of labeled calcitriol receptor for DNA-cellulose in the presence of theophylline or urate. Both theophylline and urate inhibited receptor binding affinity for DNA-cellulose. We conclude that these purine derivatives suppress calcitriol synthesis and inhibit receptor binding affinity for DNA. The altered receptor binding affinity could explain the decreased MCR of calcitriol.

Calcitriol metabolism in patients with chronic renal failure

We studied calcitriol metabolism in white patients with chronic renal failure and in age- and sex-matched normal subjects. The plasma levels of calcitriol (21.9 +/- 1.6 pg/mL, n = 7, v control, 37.4 +/- 2.9 pg/mL, P less than 0.001), metabolic clearance rate (MCR) of calcitriol (0.45 +/- .01 mL/min/kg v control, 0.58 +/- .02 mL/min/kg, P less than 0.001), and production rate (PR) of calcitriol (14.2 +/- 1.0 ng/kg/d v control, 31.8 +/- 3.2 ng/kg/d, P less than 0.001) were significantly lower in patients with moderate renal failure (average creatinine clearance, 0.59 +/- 0.01 mL/s [35.1 +/- 6.1 mL/min]) when compared with the respective values of normal control subjects. The MCR of calcitriol was determined again in patients with renal failure after they received calcitriol, 1 microgram/d, for 1 week. The MCR remained unchanged (0.46 +/- .04 mL/min/kg, n = 7) and plasma levels of calcitriol were increased to 34.6 +/- 2.77 pg/mL. The mechanism by which the MCR of calcitriol decreases in renal failure is partly due to the presence of inhibitory factors of degradation enzymes in uremic plasma. When the ultrafiltrates of uremic plasma obtained from hemodialysis patients were infused to normal Sprague-Dawley rats, the MCRs of calcitriol (0.20 +/- .01 mL/min/kg, n = 6) were markedly suppressed in comparison to those of rats infused with the ultrafiltrates of normal plasma (0.37 +/- .01 mL/min/kg, n = 6, P less than 0.001). The uremic plasma also contained factors that inhibit the synthesis of calcitriol. We conclude that metabolic degradation of calcitriol is decreased in patients with renal failure, and uremic plasma contains inhibitory factors that suppress the synthesis and degradation of calcitriol.

[Congenital cutaneous candidiasis: report of two cases]

Congenital cutaneous candidiasis is a very rare disease. We reported two newborn infants in whom generalized skin eruption was noted at birth, characteristics of erythematous papules and pustules. The eruption involved head, face, neck, trunk and extremities. Candida albicans was demonstrated on direct KOH smear, by surface fungal cultures and skin biopsy. The disease implies a congenital intrauterine infection and is different from neonatal candidiasis which manifests as thrush, diaper dermatitis. The route of infection is ascending in congenital cutaneous candidiasis. The skin eruption is usually noted at birth or within 12 hours after delivery as a diffuse erythematous maculopapula, with pustules or vesicles distributed over head, face, neck, trunk and extremities. There is no fever; other constitutional signs are lacking. No evidence of impaired immunological responsiveness has been noted in previous study. Clinical features, direct smear examination of specimen and appropriate cultures are useful in differentiating the lesions from other more common dermatoses of the neonatal period. Topical antifungal therapy is sufficient unless systemic candidiasis is present. Prognosis for congenital cutaneous candidiasis is good.

Effects of soman on calcium influx into rabbit aorta

The acute addition of 10 microM soman to rabbit aorta rings did not increase resting 45Ca2+ influx significantly in the absence or presence of 10 microM norepinephrine or 80 mM potassium (P greater than 0.05). However, agonist-induced 45Ca2+ influx into aorta rings from rabbits that received soman daily for 7 days was significantly reduced (P less than 0.05) compared to agonist-induced influx into rings from control rabbits. The resting influx of 45Ca2+ into aorta rings from 7 day soman-treated and control rabbits was not different (P greater than 0.05). The depression by soman of norepinephrine- and K(+)-induced 45Ca2+ influx may be due to adaptive changes resulting from the 7-day administration of soman.

Moderate protection of renal function and reduction of fibrosis by colchicine in a model of anti-GBM disease in the rabbit

A rabbit model of renal glomerulosclerosis induced by anti-glomerular basement membrane antibody was used to determine whether colchicine would protect renal function and reduce fibrosis. Initial studies established the time course of renal function changes and fibrosis. Colchicine at a dose of 0.02 to 0.04 mg/kg per day injected ip was begun at day 4 when injury had been initiated, and the experiment was ended at day 21 when fibrotic changes were established. Colchicine significantly reduced the rise in serum creatinine (serum creatinine = 2.7 +/- 0.3 mg% in vehicle-treated animals versus 1.8 +/- 0.1 mg% in colchicine-treated animals) and interstitial fibrosis (fibrosis score = 2.6 +/- 0.2 in vehicle-treated versus 1.5 +/- 0.2 in colchicine-treated animals). Colchicine treatment did not significantly affect weight, anti-guinea pig immunoglobulin level, % fibrocellular crescents formed, hydroxyproline per gram (dry weight) in tissue, or urine protein: creatine ratio. Regression analysis was performed to examine the interrelationships between variables for all animals and the effect of colchicine on pairs of variables. No clear-cut site of colchicine action could be identified. These data show that colchicine, in doses that could be used in humans, protected renal function by about 25% and reduced interstitial fibrosis in a model of severe crescentic nephritis.

Periventricular leukomalacia in infancy: ultrasonic diagnosis and neurological outcome

During the more than five years from January 1984 to June 1989, twenty-four patients with definite or probable cystic periventricular leukomalacia (PVL) were diagnosed by cranial ultrasonography at Mackay Memorial Hospital. The 24 patients were divided into two groups. Group A comprise two boys and four girls who received longitudinal sonographic follow-ups for leukomalacia. Of these six patients, five were premature and all suffered from severe perinatal insults. In each case, sequences of developmental cystic PVL were observed by serially scanning the brain. High echogenicity was discovered during the initial stages (2 to 7 days) in the periventricular area, and cystic formations were observed between the age of 18 and 60 days. Clinically, only one patient developed normally; four had severe motor dysfunction and poor motor development; and one was lost during follow-up, Group B was composed of 18 patients who visited the out-patient clinic for psychomotor retardation evaluation, and were found through ultrasound to have or possibly have cystic PVL formations at various stages. The clinical work-up revealed that 12 had spastic quadriplegia; 2 had hemiplegia; 3 had spastic displegia; and 1 case had hypotonic cerebral palsy. In infants, PVL is considered to be a much more reliable and important prognostic predictor than intraventricular hemorrhage. Consequently, it is crucial that physicians should screen patients at high risk for PVL, especially those with perinatal insults.

Clinical observation of meconium peritonitis

Twenty cases of meconium peritonitis were found between September 1980 and March 1988 at Mackay Memorial Hospital. The male to female ratio was 1.5 to 1. Six of the 20 cases involved premature babies. The great majority presented symptoms and signs before 5 days old, but one case was not diagnosed until 13 months of age. Polyhydramnios of the mother was found in six cases (30%). Abdominal distension was the universal symptom in all 20 cases. Hydrocele was noticed in 8 of the 12 male babies. In seven cases (35%) radiological examination showed abdominal calcifications. All patients underwent surgical intervention. Peritonitis was of cystic type in seven cases (35%); fibroadhesive in nine cases (45%); generalized in four cases (20%). Evident intestinal perforation was noted in 13 patients, and a mechanical obstructive lesion was found in 9 cases (45%) including intestinal diaphragm, atresia, volvulus, and Hirschsprung's disease. In only two patients (10%) was neither evident perforation nor obstructive lesion. The overall mortality rate was 30% (6/20), with no mortality after 1986 (0/6). The mortality seemed increased in those associated with perforation (4/13) and midgut volvulus (2/2) in particular, compared with non-perforation cases (1/7). It appears that early aggressive operation, and meticulous postoperative care, have contributed to the higher survival rate in recent years.

[Abdominal pain in diabetic ketoacidosis: report of four cases]

Four cases of diabetic ketoacidosis presenting with abdominal pain are reported. Case 1: a 14-year-old boy suffered from sudden onset of mid-abdominal pain, then migrating to the right lower quadrant. Nausea and vomiting occurred subsequently. Appendectomy was performed under the impression of acute appendicitis in an outside surgical clinic. The patient became comatose the next day and then was transferred to our hospital. Diabetic ketoacidosis was diagnosed after the detection of hyperglycemia, glycosuria, and ketonuria on the day of admission. Unfortunately, he expired on the same day in spite of vigorous resuscitation. Case 2: a 9-year-old boy complained of abdominal pain for 10 days. There was no specific finding in the physical examination. Diabetic ketoacidosis was confirmed four days later when conscious disturbance, dehydration, and tachypnea were noticed. Case 3: a 10-year-old girl presented with a history of intermittent abdominal pain for one month. The character of the abdominal pain was nonspecific. Glycosuria was detected in a pediatric clinic. Diabetic ketoacidosis was confirmed after her referral to our hospital. Case 4: a 5-year-old girl suffered from acute abdominal pain for four hours. She was found to have tachypnea, lethargy, and ill-looking. Diabetic ketoacidosis was diagnosed after serial examinations. The abdominal pain in diabetic ketoacidosis may lead the pediatrician into diagnostic error. Therefore, when a child presented with non-specific abdominal pain, a routine urine sugar should be checked in order not to miss the possibility of diabetic ketoacidosis.

Blockade of lordosis by androst-1,4,6-triene-3,17-dione (ATD) and tamoxifen in female hamsters primed with testosterone propionate

Normal female hamsters display lordosis after testosterone propionate (TP) plus progesterone (P) treatments. Such effect is probably mediated through aromatization of testosterone (T) into estradiol. If so, then an aromatase inhibitor (ATD) or an estrogen antagonist (tamoxifen, TAM) should be able to block the activational effect of T on lordosis. To test this hypothesis, 48 ovariectomized female hamsters were assigned into six groups which, according to treatments received, were ATD + TP, TAM + TP, OIL + TP, ATD + EB (estradiol benzoate), TAM + EB, and OIL + EB groups. The groups received assigned treatments for 2 days and were injected with P on the third day. Five minutes of behavior test was conducted 4 hr after P injection. The OIL + TP, OIL + EB, and ATD + EB groups all had averaged total lordosis duration (TLD) longer than 200 sec. The TLD of the TAM + EB group was only 117 sec. The ATD + TP and TAM + TP groups showed almost no lordosis. The results showed that the estrogen antagonist (TAM) impaired lordosis no matter whether the animals were primed with TP or EB, but the aromatase inhibitor (ATD) blocked lordosis only in TP primed females. It is concluded that the aromatization of T to estrogen is required for testosterone activation of lordosis in female hamsters.

Factors influencing calcitriol metabolism in renal failure

Metabolic clearance rate (MCR) and production rate (PR) of calcitriol is decreased in experimental renal failure. In this experiment, we studied uremia and secondary hyperparathyroidism as possible causes of the abnormal calcitriol metabolism. Normal rats were made uremic by infusing phosphorus-free urine for 24 hours. Both the MCR (0.22 +/- 0.01 ml/min/kg, N = 6 P less than 0.001) and the PR (16.6 +/- 1.97 ng/kg/day, P less than 0.01) of calcitriol were significantly suppressed in normal rats following urine infusion when compared to saline infused rats (MCR, 0.30 +/- 0.01; PR, 32.9 +/- 4.1, N = 6). Different levels of protein intake by rats with renal failure produced by subtotal nephrectomy also alter the PR but not the MCR of calcitriol. Thus, the synthesis of calcitriol was significantly lower in rats with renal failure fed a high protein (50% protein) diet (17.6 +/- 0.7 ng/kg/day, N = 8, P less than 0.001) than in rats with renal failure fed a normal protein (20% protein) diet (22.2 +/- 1.4, N = 7). Thyroparathyroidectomy (TPTX) did not alter the MCR of calcitriol in renal failure, even though parathyroid hormone, which may suppress the degradation enzyme, could be elevated in this model of renal failure. The MCR of TPTXed rats with renal failure (0.15 +/- 0.01 ml/min/kg, N = 7) remained lower than that of the TPTXed control rats (0.19 +/- 0.01, N = 7, P less than 0.001), and chronic infusion of PTH to TPTXed rats with renal failure did not change the MCR of calcitriol (0.15 +/- 0.01, vs. control, 0.24 +/- 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of soman in vitro on catechol-O-methyltransferase and monoamine oxidase activities in rabbit tissues

Soman (pinacolyl methylphosphonofluoridate) not only increases acetylcholine levels by inhibiting cholinesterases, it also alters the levels of some other neurotransmitters including norepinephrine, dopamine, and serotonin. Soman also causes an alteration in the activities of the enzymes metabolizing norepinephrine when it is administered to animals. Because these alterations may result from indirect effects on the enzymes, the effects of in vitro application of soman on catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO) activities in rabbit tissues were investigated. Enzyme activities were determined in rabbit lung, liver, cerebellum, cerebrum, brain stem, mesenteric artery, pulmonary artery, renal artery, central ear artery, thoracic aorta, and diaphragm. MAO and COMT activities were not affected by soman in any tissues tested, except the lung and liver, where the activity of COMT was increased (p less than 0.05). Thus, reported effects of soman in vivo on norepinephrine, dopamine, or serotonin concentrations, and MAO and COMT activities do not seem to result from direct effects on the activities of these amine-metabolizing enzymes.

Effect of polyamines, methylguanidine, and guanidinosuccinic acid on calcitriol synthesis

Previous study from our laboratory has demonstrated that infusion of uremic plasma ultrafiltrate to normal rats suppressed their calcitriol synthesis. In order identify the uremic toxins responsible for the suppression of the calcitriol synthesis, we studied the effects of known uremic toxins: spermidine, spermine, methylguanidine (MG), and guanidinosuccinic acid (GSA) on calcitriol metabolism in the rats. Metabolic clearance rate (MCR) and production rate (PR) of calcitriol were measured in normal rats after they were infused for 24 hours with approximately 10 ml of normal saline containing one of the following substances: 0.8 mumoles spermidine, 0.3 mumoles spermine, 150 micrograms MG and 180 micrograms GSA. Control groups of rats were infused with 10 ml of normal saline for 24 hours. MCR of calcitriol was not altered by the infusion of each toxin; however, plasma concentration of calcitriol (controls, 105.3 +/- 6.7 pg/ml; versus GSA, 58.9 +/- 2.5 pg/ml, p less than 0.001) and PR of calcitriol (controls, 39.0 +/- 2.9 ng/kg/day, versus GSA, 22.5 +/- 1.62 ng/kg/day, p less than 0.001) were significantly suppressed by the infusion of GSA. The concentration (1.8 mg/dl) of GSA in the infusate was similar to that in the uremic plasma ultrafiltrate (2.32 +/- 1.41 mg/dl) used in the previous study, though the total amount of GSA infused to the rats was lower in the present study. GSA is, therefore, considered a uremic toxin that suppresses calcitriol synthesis.

Apolipoproteins A-I and B in non-insulin-dependent diabetes mellitus

In recent years apolipoproteins A-I and B examinations have been performed on patients with coronary artery disease as a better predictor of the severity of atherosclerosis. In the present study, 21 treated male and 22 treated female patients with non-insulin-dependent diabetes mellitus (NIDDM) were examined and compared with controls of the same sex, age and body mass (23 males, 21 females). Cholesterol, triglyceride, LDL-cholesterol in male and female patients with NIDDM were significantly higher than in male and female controls. HDL-cholesterol in male and female patients with NIDDM was not different from those of male and female controls. Apolipoproteins A-I and B in male and female patients with NIDDM were higher than in male and female controls. [Apolipoproteins A-I (g/L) male 1.40 +/- 0.21 vs 1.25 +/- 0.15, p less than 0.005; female 1.56 +/- 0.23 vs 1.42 +/- 0.24, p less than 0.025. Apolipoproteins B (g/L) male 1.29 +/- 0.30 vs 0.97 +/- 0.22, p less than 0.001; female 1.34 +/- 0.34 vs 0.98 +/- 0.35, p less than 0.001.] Discrepancy between the higher apolipoprotein A-I and the normal HDL-cholesterol in in NIDDM supports the theory of altered composition of HDL particles in diabetic patients. The controversy between the higher apolipoprotein A-I and the higher incidence of atherosclerosis in patients with NIDDM makes the clinical usefulness of this laboratory measurement doubtful in these patients.

The role of osmolarity in renin release from afferent arterioles

We studied the role of sodium (Na) in renin release from isolated afferent arterioles incubated in Krebs-Ringer bicarbonate solutions with the Na concentrations adjusted to 145, 135, 125, 110 and 95 mmol/l. The arterioles were incubated for three consecutive periods, with the sequence of incubations randomized. Renin release increased by 119 and 275% in the media with Na concentrations of 135 and 125 mmol/l, respectively, as compared with the renin released from arterioles incubated in the medium with Na 145 mmol/l. When the Na concentrations of the incubation media were further lowered to 110 mmol/l and 95 mmol/l, renin release continued by 118 and 216%, respectively, in comparison with that in the medium having an Na concentration of 125 mmol/l. Regression analysis showed that renin release increased by 98% for each 10 mmol/l decrement of Na concentration. When the osmolarity of the incubation medium was held constant, varying the Na concentrations did not alter the renin secretion. This suggests that renin was released from the arterioles in response to the osmotic pressure exerted by Na rather than as an ionic effect. Renin release was suppressed by the osmotic effects of sucrose and urea, although the suppressive effect of urea was weaker.

Effect of vitamin D metabolites on calcitriol metabolism in experimental renal failure

Previous studies from our laboratory have demonstrated that metabolic clearance rate (MCR) of calcitriol is decreased in experimental renal failure. In this experiment, we examined the effects of calcitriol, 25-hydroxyvitamin D3 (25(OH)D3) and 24,25-dihydroxyvitamin D3 (24,25(OH)2D3) on the MCR of calcitriol in renal failure produced in rats by partial nephrectomy. The MCR of calcitriol in these rats with renal failure was significantly lower than in control rats with sham operations. Plasma concentrations of calcitriol did not differ between the rats with moderate renal failure and control rats (sham, 74.7 +/- 3.6 pg/ml, N = 7; renal failure, 67.7 +/- 6.0, N = 6; serum creatinine 0.56 +/- 0.02 mg/dl vs. 0.96 +/- 0.02); however, the levels were significantly lower in rats with severe renal failure (sham, 66.5 +/- 5.1 pg/ml, N = 7, severe renal failure, 49.6 +/- 2.1 pg/ml, N = 8; serum creatinine 0.53 +/- 0.01 mg/dl vs. 1.40 +/- 0.03). Subcutaneous infusion of calcitriol (10 ng/kg/day) in rats with severe renal failure for one week significantly increased the MCR of calcitriol (0.22 +/- .01 vs. 0.17 +/- .01 ml/min/kg, P less than 0.001). Infusion of 25(OH)D3 (600 ng/day) or 24,25(OH)2D3 (1 microgram/day) in rats with renal failure for one week also increased the MCR of calcitriol (25(OH)D3, 0.25 +/- 0.01 ml/min/kg; 24,25(OH)2D3, 0.25 +/- 0.01, both P less than 0.001) when compared to rats with renal failure infused with vehicle (0.21 +/- 0.01). Administration of 24,25(OH)2D3 significantly lowered the plasma levels of calcitriol in rats with renal failure (52.3 +/- 3.1 pg/ml, P less than 0.05) in comparison to the rats with renal failure infused with vehicle (67.7 +/- 6.0).(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of theophylline and cyclic adenosine 3',5'-monophosphate on renin release by afferent arterioles

The effects of theophylline and cyclic adenosine 3',5'-monophosphate (cAMP) on renin release by afferent arterioles were studied. Rabbit afferent arterioles (seven to 10), obtained by a microdissection technique, were incubated for three consecutive 20 min periods in 100 microliters of Medium 199 with 0.1% bovine serum albumin (BSA). Afferent arterioles exposed to theophylline, 1 x 10(-4) mol/l, produced a greater than 100% increase in renin release (0.18 +/- 0.04 to 0.42 +/- 0.05 ng angiotensin l/h per arteriole per h incubation). The renin release stimulated by theophylline was completely abolished by indomethacin and meclofenamate. The stimulation of renin secretion was also blocked when extracellular calcium concentration was decreased to 10(-7) mol/l and the arterioles were permeabilized with calcium ionophore. Dibutyryl cAMP (db-cAMP), 1 x 10(-4) mol/l, and forskolin, 1 mumol/l or 100 mumol/l, failed to stimulate renin release by afferent arterioles. The results of this study therefore suggest that theophylline-stimulated renin release may be mediated through a prostaglandin pathway. The stimulation of renin secretion is also dependent on the extracellular concentration of calcium.

Limitation of the alpha-methylnorepinephrine hypothesis in the hypotensive effect of alpha-methyldopa

To test the hypothesis that alpha-methylnorepinephrine (MNE) is the principal active metabolite involved in the hypotensive action of alpha-methyldopa (MD), we determined the relationship between MD's depressor response and tissue levels of MD metabolites in critical sites. After administration of 250 mg/kg MD intraperitoneally to Sprague-Dawley rats (300 +/- 50 g), we studied both heart (left ventricle) and brainstem MD, MNE and endogenous NE levels using HPLC with electrochemical detection. We also measured systolic blood pressure before and during MD (25-250 mg/kg i.p.) treatment using the tail-cuff method. Our results indicate that: (1) peak MD hypotensive response was dose-dependent. (2) Central NE concentration was maximally reduced by 2 hours whereas peripheral NE was maximally reduced by 18 hours. The maximal hypotensive effect was closer to the central peak distribution of MNE than MD. (3) The MD concentrations and NE concentrations in brainstem and heart showed counterclockwise hysteresis while MNE showed clockwise hysteresis. Furthermore, the area of MNE hysteresis in brainstem was larger than that of NE. We conclude that MD's depressor effect can not be completely explained by the assumption that MNE is the sole active metabolite; alternate metabolites or mechanisms would appear to be operative.

Is skeletal response to parathyroid hormone abnormal in experimental renal failure?

It is widely believed that skeletal resistance is the mechanism of impaired calcemic response to parathyroid hormone (PTH) in renal failure. The action of PTH not only involves skeletal mobilization of Ca, it may also stimulate intestinal absorption of Ca and renal conservation of Ca. We have examined each of these factors and studied the calcemic response to PTH in renal failure. PTH, 3 U/hr/100 gm, was infused for 5 hours in rats with renal failure 3 weeks after a five-sixths nephrectomy. In nonfasted animals, the post-PTH increments of total plasma Ca (0.71 +/- 0.06 mg/dl) and ionized Ca (0.37 +/- 0.06 mg/dl) of control sham-operated rats were significantly greater than those of rats with renal failure (plasma Ca 0.37 +/- 0.02 mg/dl and plasma ionized Ca 0.17 +/- 0.01 mg/dl both p less than 0.001). Urinary Ca excretion rate remained unchanged during PTH infusion despite the increase in plasma Ca. Plasma levels of calcitriol after PTH injection were higher in control rats (257 +/- 18 pg/ml) than in rats with renal failure (162 +/- 5 pg/ml, p less than 0.001). Pretreatment of rats with renal failure with 50 ng calcitriol intravenously corrected the abnormal calcemic response to PTH. To exclude the PTH effect on intestinal Ca absorption, PTH infusion was carried out in animals fasted for 18 hours. The post-PTH increments of Ca were no longer different between rats with renal failure (plasma Ca 0.37 +/- 0.04 mg/dl, plasma ionized Ca 0.20 +/- 0.01 mg/dl) and control rats (plasma Ca 0.37 +/- 0.03 mg/dl, plasma ionized Ca 0.19 +/- 0.01), suggesting that skeletal mobilization of Ca was similar between the two groups of animals. We conclude that lack of intestinal response to PTH rather than skeletal resistance was the mechanism of impaired calcemic response to PTH in this model of renal failure.

Calcitriol synthesis is decreased in spontaneously hypertensive rats

To investigate the mechanisms of abnormal calcium metabolism, such as hypocalcemia, decreased intestinal calcium absorption and hypercalciuria in spontaneously hypertensive rats (SHR), we have measured the plasma concentration of calcitriol and its synthesis in 5-, 8-, 12-, 16-, and 20-week-old normotensive Wistar Kyoto rats (WKY) and SHR. Metabolic clearance rate (MCR) and production rate (PR) of calcitriol were measured by the constant isotope infusion method. Plasma concentration of calcitriol and PR of calcitriol were decreased in SHR after 12 weeks of age. MCR of calcitriol, however, was not different between WKY and SHR in any age group. Therefore, the decreased synthesis of calcitriol accounts for the lower plasma level of calcitriol in SHR after 12 weeks of age. Metabolic acidosis or decreased renal function could not account for the decreased synthesis of calcitriol, since the blood pH and pCO2 and creatinine clearance were similar between WKY and SHR at times when the calcitriol synthesis was reduced in SHR. Plasma concentration of ionized calcium was also lower in SHR after 12 weeks of age. Plasma concentration of calcitonin was significantly higher in 16-week-old SHR (41.6 +/- 1.5 pg/ml) than in age-matched WKY (30.5 +/- 1.7, P less than 0.001). The values, however, were not different between 8- and 12-week-old WKY and SHR. We believe that the decreased synthesis of calcitriol could be the pathogenetic factor for the development of abnormal calcium metabolism in SHR. Age of animals should be considered when studying the calcium metabolism in SHR.