THE EFFECT OF SPIRONOLACTONE ( ALDACTONE ) ON ELECTROLYTE BALANCE AND RENAL FUNCTIONS OF CALVES

Skrzypczak W. F., K. Janus, Z. Muszczynski and D. Jankowiak: The effect of spironolactone (Aldactone) on electrolyte balance and renolfuncions of calves. Acta vet. Bmo, 63, 1994: 19-23. A short spironolactone test was carried out in a group of 10 clinically healthy calves at the age of 4 weeks. For 5 days (every 24 hours) the calves were administered Aldactone (Searle), per os, at a dose of 1 mglkg of body weight. Before the test began and 120 and 144 hours after giving the first spironolactone dose, the effective renal blood (ERBF) and plasma (ERPF) flow, and the glomerular filtration rate (GFR) were measured using sodium salt of p-aminohippuric acid and inulin. The levels of sodium, potassium and chlorides in plasma and erythrocytes were also determined. Some changes in the concentration of tested electrolytes were found in both the plasma and the intracellular fluid of erythrocytes. Changes in the renal function of calves were also indicated by an increase in effective renal plasma flow as well as by a decrease in glomerular filtration rate. Spironolactone, electrolyte b(llance, renal.fi!,nction, calves Calf kidneys are functionally efficient in the fIrst month oflife. However, they reveal some features of functional immaturity. These involve lowered effective renal blood (ERBF) and renal plasma (ERPF) flow,low glomerularfiltrationrate and low ability of urine concentration (Mercer etal.1978; Wanner etal.1981; Hartmann et al. 1987; Skrzypczak 1989; Skrzypczak etal. 1989; Skrzypczak 1991). The observed high tabular resorption ofNa, K and Cl in the frrst ~ days of life (Safwate et al., 1980; Skrzypczak, 1991) becomes lower as the age of calves increases (Safwate etal.1982; Skrzypczak 1989). The results of experiments show that, by the third day of life, mechanisms which control sodium resorption become active and kidney tubules respond to aldosterone infusion with the growth ofNa resorption (Safwate et al. 1980; Safwate et al. 1982; Itoh et al. 1985; Safwate 1985). Some authors, however, found a lack of correlation between the plasma renin activity and the aldosterone level, and sodium and potassium concentrations in the blood plasma (Siegler etal.1977; Moncaup etal.1980; Safwate etal.1982). Cabello (1980)evenreportsanegative correlation between plasma levels of aldosterone and sodium. Jankowiak (1989) showed that administering DOCA at a dose of 0.1 mglkg body weight Lm. caused a clearance drop and the urine excretion of sodium, potassium and chlorides also decreased. Safwate (1985) also noticed a lowering of sodium excretion in urine after aldosterone infusion, although he did not observe any changes in potassium excretion. Some authors indicate that there is a possibility of metabolic stimulation of the calf suprarenal glands in the first month of life (McEwan et al. 1968; Baranow-Baranowski etal. 1987). As can be seen from the literature review, there are many issues connected with tubular activity regulation in the postnatal period pertaining to electrolytes resorption which have not been fully explained yet (K a g a w a 1960; Bra u n Ii chand K e r s ten 1972; Cor v 0 I et al. 1981). The objective of this paper was to examine the effect of spironolactone (Aldactone) on electrolyte balance of body fluids and on glomerular filtration rate and effective blood and plasma flow through young calf kidneys. Materials and Methods The experiment was carried out on a group of 10 clinically healthy calves of cb. breed at the age of 4 weeks. They were kept in a calf-pen under constant, optimal conditions. Their left and right jugular vein had been catheterized and they had been weighed before the experiment began. Prior to the treatment period, the effective renal plasma (ERPF) and blood (ERBF) flow and the glomerular filtration rate (GFR) were defined. The levels of sodium, potassium and chlorides in blood plasma and erythrocytes were examined. To assess ERPF and GFR, sodium salt of p-aminohippuric acid (Serva-GmbH) and inulin (Sigma Chern. Co.) were used respectively. The clearance of these substances was measured using Bettge' s method. On the basis of ERPF and haematocrit, the amount of ERBF was defined and the filtration fraction (FF) was calculated. In order to block aldosterone activity, a short spironolactone test was conducted. The calves were administered 1 mglkg body weight of Aldactone (Searle) per os for 5 days. After 120 and 144 hours from giving the first dose of Aldactone, new examinations of ERPF, GFR values and Na, K and Cllevels in plasma and whole blood were carried out.

The results of experiments show that, by the third day of life, mechanisms which control sodium resorption become active and kidney tubules respond to aldosterone infusion with the growth ofNa resorption (Safwate et al. 1980;Safwate et al. 1982;Itoh et al. 1985;Safwate 1985).Some authors, however, found a lack of correlation between the plasma renin activity and the aldosterone level, and sodium and potassium concentrations in the blood plasma (Siegler etal.1977;Moncaup etal.1980;Safwate etal.1982).Cabello (1980)evenreportsanegative correlation between plasma levels of aldosterone and sodium.Jankowiak (1989) showed that administering DOCA at a dose of 0.1 mglkg body weight Lm. caused a clearance drop and the urine excretion of sodium, potassium and chlorides also decreased.Safwate (1985) also noticed a lowering of sodium excretion in urine after aldosterone infusion, although he did not observe any changes in potassium excretion.Some authors indicate that there is a possibility of metabolic stimulation of the calf suprarenal glands in the first month of life (McEwan et al. 1968;Baranow-Baranowski etal. 1987).
As can be seen from the literature review, there are many issues connected with tubular activity regulation in the postnatal period pertaining to electrolytes resorption which have not been fully explained yet (K a g a w a 1960; Bra u n Ii chand K e r s ten 1972; Cor v 0 I et al. 1981).The objective of this paper was to examine the effect of spironolactone (Aldactone) on electrolyte balance of body fluids and on glomerular filtration rate and effective blood and plasma flow through young calf kidneys.

Materials and Methods
The experiment was carried out on a group of 10 clinically healthy calves of cb.breed at the age of 4 weeks.They were kept in a calf-pen under constant, optimal conditions.Their left and right jugular vein had been catheterized and they had been weighed before the experiment began.
Prior to the treatment period, the effective renal plasma (ERPF) and blood (ERBF) flow and the glomerular filtration rate (GFR) were defined.The levels of sodium, potassium and chlorides in blood plasma and erythrocytes were examined.To assess ERPF and GFR, sodium salt of p-aminohippuric acid (Serva-GmbH) and inulin (Sigma Chern.Co.) were used respectively.The clearance of these substances was measured using Bettge' s method.On the basis of ERPF and haematocrit, the amount of ERBF was defined and the filtration fraction (FF) was calculated.In order to block aldosterone activity, a short spironolactone test was conducted.The calves were administered 1 mglkg body weight of Aldactone (Searle) per os for 5 days.After 120 and 144 hours from giving the first dose of Aldactone, new examinations of ERPF, GFR values and Na, K and Cllevels in plasma and whole blood were carried out.
The colorimetric method was used for determination of inulin levels based on the fructose amount (Tomaszewski, 1970), and Wangh and Beall's method was used to measure P AH plasma levels (Wangh and Beall 1974).Sodium and potassium concentrations were determined using the photometric method (Flaph0-4) and chlorides were assessed using the potentiometric method (Chlorimetr Spexon-l00).The concentration of ions in erythrocytes was calculated according to the following formula: where: S = body surface, m. c. = body weight (Skrypczak 1989).
Statistical significances were calculated using D-Duncan's test.

Results and Discussion
The effect of administering Aldactone is that it blocks mineralocorticoid receptors in tubules and decreases aldosterone biosynthesis (C 0 r v 0 I et al. 1981) by lowering the number of open sodium canals (Horisberger and Giebisch 1987).The results obtained show that, in the calves, Aldactone caused a change in the mineral status, first of all in the extracellular fluid space.
The levels of Na, K and CI in blood plasma and erythrocytes before the experiment were approximately the same as other authors have observed (Kucera et al.1977;Safwate et al. 1982; Bar a now -Bar a now ski et al. 1988).Aldactone administration caused a decrease of sodium level and an increase ofK concentration in blood plasma (P<O.OI).The concentration of chloride ions also decreased considerably although statistical differences at the P < 0.05 level were not obtained (Table 2).Some changes in the mineral profile of intracellular erythrocyte fluid were also recorded (Table 3).The inhibition of the antinatriuretic aldosterone effect lowered the concentration of sodium significantly.The increase of the haematocrit indicator (P < 0.01) points to a decrease of blood plasma volume, which was probably caused by increased Na, CI and water excretion in urine (Table 1).
The renal plasma and blood flow and the glomerular filtration rate before Aldactone administration (Table I) had been at comparable levels with the results obtained by other authors (Meercer etal.1976;Wanner etal.1981;Hartman etal.1967).Intheexperiment there was also an indication that the changes in mineral status and the changes in plasma volume, caused by Aldactone administration, modified the renal function.Although the significance of the changes in blood and plasma flow was not statistically confirmed at the P < 0.05 level, their biological importance in the whole process of maintaining water-electrolyte homeostasis was evident.It seems that the observed increase in blood flow through the kidneys (Table 1) is connected with the inhibition the renin-angiotensis system caused by an increase in the amount of sodium in distal tubules.Perhaps, this is due to changes in blood flow through the renal medulla.The lowered ERPF, in spite of increased ERBF, was connected with the decreased blood plasma volume.In parallel with the ERPF decrease, GPR also decreased, which is evident in the stable amount od the filtration fraction (Table 1).This renal response may constitute a "compensatory" mechanism which limits the amount of sodium chloride excreted in urine.
In conclusion, there appeared to be marked aldosterone activity in 4-week-old calves which could be inhibited by administration of Aldactone.This, in turn, caused increased renal excretion of Na and Clleading to a decrease in their levels in blood plasma and erythrocytes.There was also a decrease in plasma volume.The water -electrolyte changes in the extracellular fluid affected renal function reversibly, modifying blood flow through the kidneys and the glomerular filtration rate.This constitutes a mechanism limiting electrolyte excretion in urine.