Antidiuretic hormone infusion reduces taurine and NaCl-induced hypernatremia in the rat.

Rats drinking taurine and hypertonic saline (T + S) develop severe hypernatremia, but rats drinking either T or S alone do not. One hypothesis for this disruption of homeostasis is that the T + S combination interferes with the actions of antidiuretic hormone (ADH). Rats drinking T + S developed severe hypernatremia (170 mmol/L) by day 8 when infused with distilled water by osmotic minipumps, but maintained plasma sodium below 150 mmol/L when infused with ADH. Cumulative water balance in T + S drinkers receiving ADH was consistently higher than in those not receiving ADH. However the ratio of cumulative sodium balance to cumulative water balance suggests little uniform advantage to rats receiving ADH nor does comparison of urine osmolality in the two groups. Precisely how ADH administration reduces hypernatremia in T + S drinking rats remains unclear, but the hypothesis that T + S interferes with the action of ADH in its regulation of extracellular fluid volume and osmolality remains viable.

beta-Alanine protects against taurine and NaCl--induced hypernatremia in the rat.

Rats drinking a combination of taurine and hypertonic saline solution rapidly develop hypernatremia, but rats drinking either solution alone do not. The mechanism by which taurine disrupts the ability to deal with a salt load is not clear. Rats housed in metabolism cages were studied. Food intake, fluid intake, plasma sodium concentration, urine output, sodium balance, visible water balance, and urine osmolality were determined over a period of 8 days. Rats drinking 0.1 M taurine plus 1.8% NaCl developed a mean plasma sodium concentration of 160 +/- 18 mM by Day 6, compared with 137 +/- 1.6 mM in water drinking controls. Ingestion of 1.8% saline alone produced only a mild, transient rise in plasma sodium (<150 mM), which returned to control levels by Day 8. Ingestion by neither 0.1 M taurine alone nor 0.1 M beta-alanine, a taurine transport antagonist, produced any evidence of hypernatremia throughout the experiment. When beta-alanine was added to the taurine + saline regimen, mean plasma sodium reached only 149 +/- 16 mM (Day 6). Inspection of the ratio of cumulative sodium balance to cumulative water balance revealed a rapid increase until Day 2, followed by a virtual plateau thereafter in the taurine + saline group. Rats drinking saline alone showed an equally rapid rise in the ratio, but to a lower plateau level, suggesting that taurine exerts a much more pronounced disturbance of sodium balance than of water balance. The addition of beta-alanine to the regimens of taurine + saline or saline alone produced ratios of cumulative sodium to cumulative water balance significantly lower than that of either regimen without beta-alanine. These findings suggest that taurine induces hypernatremia by interfering with normal homeostatic control mechanisms and that beta-alanine counteracts that action of taurine. The effect of beta-alanine in rats drinking saline alone is consistent with a role for endogenous taurine in normal electrolyte homeostasis.

Effects of unilateral nephrectomy during early pregnancy.

Litter data and kidney growth parameters in Wistar rats uninephrectomized (UNX) or sham-operated (SO) on the 5th-7th day of gestation, and in unoperated controls (C) were investigated at 1 day and at 6 wk postpartum. Gestation period, litter size, sex ratio of pups, and pup weight at birth did not differ among the groups. At 6 wk, pups from UNX mothers displayed retarded growth. Compensatory kidney growth following UNX in pregnant rats was predictable for wet weight, but dry weight compensation was transient and limited.

Atrial natriuretic factor in taurine-treated normal and cardiomyopathic hamsters.

Diuretic and natriuretic activities of atrial extracts from BIO 14.6 (cardiomyopathic) and F1B (normal) hamsters at 180 days of age were measured by rat bioassay. Both activities were lower in BIO 14.6 extracts. Because of the reported protective action of taurine in the cardiomyopathic hamster, we tested the effect of 0.1 M taurine drinking upon the activity of atrial extracts. Urine flow and Na+ excretion were increased in both BIO 14.6 and F1B; however, comparatively larger increases in BIO 14.6 taurine drinkers abolished strain differences that were observed in water drinkers. Taurine drinking BIO 14.6 hamsters exhibited an increased plasma sodium concentration. Drinking of 0.6% NaCl also produced an elevated plasma sodium concentration in BIO 14.6. Extracts from hamsters with increased salt intake had diuretic and natriuretic activities that were not different from those of water drinkers. These findings confirm that ANF activity is deficient in BIO 14.6 hamsters, and this suggests a role for taurine in its production, release, and/or activation.

Exchangeability of heart calcium in cardiomyopathic hamsters.

Acute electrolyte depletion markedly reduced the elevated heart calcium in 60-day-old BIO 14.6 hamsters. This exchangeability may explain the susceptibility of calcium to therapeutic intervention at 60 days. At 120 days, the procedure did not alter heart calcium concentration.

Ethanol-induced sleeping time in mice: age and sex differences.

Ethanol-induced sleeping time was determined in mice of both sexes at ages ranging from 3 weeks to just over 1 year. A progressive increase in sleeping time was seen in both sexes up to 26 weeks of age; no subsequent changes were observed, except for a modest decrease in the oldest female group. In the majority of age groups, sleeping time values were higher in females, but few statistically significant sex differences were found.

Comparison of soft tissue calcium levels throughout the life spans of normal and myopathic hamsters.

Comparisons of calcium levels in heart, skeletal muscle, brain, liver and plasma were made throughout the life spans of normal and genetically myopathic hamsters. A large calcium accumulation occurred in, and was restricted to, myopathic tissues (heart and skeletal muscle). Calcium elevation in myopathic tissues corresponded to documented lesion appearance, and persisted throughout the remainder of the life span. Calcium buildup in heart and skeletal muscle, as a central feature of the myopathic process, does not reflect a general failure of calcium homeostasis; nonmyopathic tissues are unaffected. Calcium increased moderately in some normal tissues late in life.

Kidney growth and collagen content in rat pups from uninephrectomized mothers.

The effect of uninephrectomy (UNX) or sham-operation (SO) in pregnant rats at the 5th-7th day of gestation upon pup kidney development was studied. In newborns, kidney wet weight was low in pups of the SO and UNX groups, kidney/body weight was low in UNX only; collagen was highest in UNX. At 6 weeks, wet weight was least in UNX; dry weight was low and %H2O high in SO and UNX; collagen/dry weight was high in SO and UNX. Maternal surgery (SO or UNX) appears to impose a non specific development deficit upon pups, although kidney collagen growth is sustained; no specific renotropic activity was evident in pups of the UNX groups.

Taurine and ethanol-induced sleeping time in mice: route and time course effects.

Taurine was given to mice: (i) intracerebroventricularly (i.c.v.) 20 min prior to 4.5 g/kg of ethanol intraperitoneally (i.p.); (ii) i.p. 10 min-5 days prior to ethanol; or (iii) orally (p.o.) as drinking fluid for 30 days prior to ethanol. Ethanol-induced sleeping time was increased by i.c.v. taurine and also by i.p. taurine when the pretreatment interval was 4-5 days. The long i.p. pretreatment time probably reflects the slow uptake of taurine by the brain. Sleeping time was decreased by p.o. taurine and by i.p. taurine when the pretreatment interval was 10-20 min. The mechanism of this attenuation remains unclear.

Effects of verapamil and taurine administration on heart taurine and calcium in BIO 14.6 cardiomyopathic hamsters.

Administration of either taurine or verapamil raised heart taurine and reduced heart calcium levels in BIO 14.6 hamsters. Combined administration of the two agents magnified both effects. It is suggested that the marked reduction of heart calcium produced by verapamil may be partially mediated through the membrane-stabilizing, calcium-modulating actions of taurine at the sarcolemma.

Comparison of taurine-verapamil interaction in hamsters and rats.

Taurine concentrations were determined in hearts and whole blood of female Syrian golden hamsters and Wistar rats following 30 days of drinking: (i) tap water, (ii) taurine solution or (iii) a taurine uptake inhibitor (GES). The groups were duplicated in animals receiving daily verapamil injections during the treatment period. Heart taurine increased with (ii) and decreased with (iii) in both species; blood taurine changed similarly in rats only. Verapamil enhanced taurine uptake and offset the GES inhibition in the hamster heart, but had no such effect in rats. Possible implications of the species differences are elaborated upon.

Effects of taurine and verapamil on heart calcium in hamsters and rats.

Heart calcium was measured in hamsters and rats following 30 days of drinking (i) tap water, (ii) taurine solution (T) or (iii) a taurine uptake inhibitor (GES). The regimes were duplicated in animals receiving verapamil (V). Heart calcium was reduced in both species by T + V; a comparable effect was obtained with GES alone; T alone had no effect. In the hamster, the GES effect was reversed by GES + V; V alone had no effect. In rats, the separate and combined effects of GES and V on heart calcium were identical. Possible mechanisms and underlying species differences are discussed.

Compensatory kidney collagen growth vs. age in uni-nephrectomized rats.

Kidney collagen content, wet and dry weights, were measured in male Wistar rats unilaterally nephrectomized (NX) at ages ranging from 3-52 weeks. The compensatory responses in the contralateral kidney were assessed at eight (NX + 8) and 16 (NX + 16) weeks post-operatively; the (NX) values were compared with those from sham-operated controls at the same age and post-operative time. Both (NX) and sham (S) values were contrasted to the normal kidney growth parameters of unoperated control (C) rats. Kidney wet weight in the (NX) group was greater than that in either (S) or (C) and the major part of the compensatory growth occurred in the (NX + 8) period. In younger rats (12 weeks at NX), the dry weight response was like that of net weight, but in older animals the dry weight compensation had a generally slower onset. The compensatory growth of collagen in younger (NX) rats was greater than that seen in (S), and (S) was the same as (C). In older rats, (NX) and (S) collagen were not different, but both were much higher than (C). The finding that older animals, unlike young ones, increase their kidney collagen in response to surgery, with or without a loss of renal tissue, points to a nonspecific stimulus for collagen growth and suggests that, in older rats, the turnover equilibrium of collagen is shifted toward synthesis under such conditions.

Soft tissue potassium, magnesium, sodium and ash contents throughout the life span of highly inbred rats.

K, Mg, Na and ash contents were determined in nine tissues from short-lived Fischer rats at ages ranging from 1-21 months and from longer-lived A X C rats ranging from 1-28 months. K and Mg generally declined with aging in the tissues of both rat strains with higher rates of decline occurring in the shorter-lived Fischer rats. Na showed no consistent, strain-specific changes, but the majority of observed changes were age-related declines. Tissue ash contents generally declined during aging with the longer-lived A X C rats showing larger decreases.