Inhibitors of 11 beta-hydroxysteroid dehydrogenase and 5 beta-steroid reductase in urine from patients with congestive heart failure.

Recently, the current authors reported the presence in normotensive male and female urines of reproducibly measurable levels of naturally occurring substances in partially purified extracts of urine with inhibitory activity like glycyrrhetic acid (GA) towards both 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD) and steroid 5 beta-reductase (5 beta-SR) in vitro. Since these substances mimic two known inhibitory activities of GA, they have been named 'Glycyrrhetic Acid-Like Factors', abbreviated as 'GALFs' or, more specifically 11 beta-GALF for substance(s) active against 11 beta-OHSD, and 5 beta-GALF for those inhibitory to 5 beta-SR. Administration of glycyrrhetic acid in man leads to cortisol-dependent mineralocorticoid hypertension, owing to impaired inactivation of cortisol by 11 beta-OHSD, and may be associated with increased sensitivity to mineralocorticoids owing to impaired 5 beta-SR. In this preliminary report, the results are described of a study on the presence of GALF factors in urines collected from patients with congestive heart failure (CHF) and mild essential hypertension. The results show that in such patients there are increased amounts of both 11 beta- and 5 beta- GALFs compared to normotensive. The possible physiological significance of these results is discussed.

Effects of carbenoxolone administered acutely to adrenalectomized rats (in vivo) on renal and hepatic handling of corticosterone by 11 beta-hydroxysteroid dehydrogenase.

The in vivo effect(s) of carbenoxolone (CS) on renal 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD), hepatic 11 beta-OHSD, and 5 beta-reductase enzymatic activity was investigated, under conditions previously shown to confer mineralocorticoid (MC)-like activity on the glucocorticoids cortisol and corticosterone; it has been suggested that this Na+ retention is linked to inhibition of renal 11 beta-OHSD. The results show that acute administration of CS [2.5 mg/rat for 0.5 or 2 hours; and 10 or 25 mg/rat for 2 hours subcutaneously (sc)] to rats caused no inhibition of 11 beta-OHSD activity in kidney homogenates, minces, and microsomes when compared with controls. However, addition of 50 nM CS to the incubation medium completely inhibited the 11 beta-OHSD activity in kidney homogenates and microsomes (from controls or CS-injected rats). In contrast, hepatic microsomal 11 beta-OHSD was significantly inhibited after in vivo treatment with CS (P < 0.05) using 2 microM and 50 microM corticosterone, as was 5 beta-reductase (P < 0.05) using 4 microM corticosterone as substrate. However, chronic glycyrrhizin administration (15 mg/rat/day sc for 14 days) significantly inhibited renal 11 beta-OHSD activity when assayed in minces or homogenates. Thus, it appears that when CS is administered acutely, its effects are primarily on hepatic 11 beta-OHSD and 5 beta-reductase with no inhibition of renal 11 beta-OHSD.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of glycyrrhetinic acid-like factors (GALFs) in human urine.

Patients with the syndrome of apparent mineralocorticoid excess and those who ingest licorice show markedly decreased 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD) and 5 beta-reductase activity; both are important for the deactivation of glucocorticoids and other steroid hormones. Glycyrrhetinic acid (GA), present as its glycoside in licorice, is a potent inhibitor of both 11 beta-OHSD and 5 beta-reductase and, as we have also shown, confers Na(+)-retaining properties on glucocorticoids and amplifies those of aldosterone and deoxycorticosterone. We report the results of our initial studies demonstrating the presence of naturally occurring substances, which inhibit both 5 beta-reductase and 11 beta-OHSD as does GA, in partially purified extracts of urine from normotensive men and nonpregnant and pregnant women. Since these substances exhibit GA-like activity, we have termed them GA-like factors (GALFs). This "inhibitory" material is heat stable and does not react with ninhydrin; the majority is not extractable with ethyl acetate and thus is not a "free" steroid. When further purified by high-performance liquid chromatography with a methanol/water gradient, the majority of these GALFs appeared in two regions of inhibitory activity. The chemical nature of this material is currently being investigated. These experiments indicate that normal human urine contains GALFs that may play a role in Na+ homeostasis and regulation of blood pressure.

Depletion of essential elements by calcium disodium EDTA treatment in the dog.

The effect(s) of calcium disodium ethylenediaminetetraacetate (CaNa2EDTA) on the metabolism of Zn, Cu and Mn was investigated in mongrel female dogs. Dogs received either CaNa2EDTA (0.75 mmol/kg subcutaneously) or 0.9% NaCl (controls). Urine was collected every 6 h. Tissue samples were obtained from liver, kidney, duodenum, muscle, hair, skin and bone post exsanguination. CaNa2EDTA treatment increased urinary excretion of Zn, Cu and Mn, significantly when compared to controls (P less than 0.05, n = 5). Furthermore, CaNa2EDTA either decreased Zn levels (hair, duodenum, skin) and Mn levels (hair) or increased Cu levels in kidneys (P less than 0.05). These data suggest that the sustained urinary loss of Zn, Cu and Mn was probably associated, in part, with mobilization and redistribution of these essential elements from storage tissues as well as soft tissues. It was concluded that the use of calcium disodium EDTA for the management of heavy metal poisoning in dogs could adversely affect the metabolism of essential elements, particularly Zn, Cu and Mn.

Effect of high calcium diet on the development of high blood pressure in intact spontaneously hypertensive rats and in adrenalectomized spontaneously hypertensive rats treated with aldosterone.

The current investigation was designed to study the effect(s) of high calcium diet on the development of high blood pressure (BP) in both young intact spontaneously hypertensive rats (SHRs) and in young adrenalectomized (ADX) male SHRs treated with aldosterone (ALDO). Weaned SHRs were fed either a control calcium diet (0.5% Ca as PO4) (CCaDiet), a high calcium diet (2.5% Ca, 0.5% as PO4 and 2% as CO3) (HCaDiet), or Agway ProLab rat food containing 2.5% Ca (HCaPLDiet). The HCaDiet significantly blunted the development of high BP in young intact SHRs (P less than 0.001; n = 8 to 10). At 6 weeks of age, BP was 117 +/- 2 mm Hg (HCaDiet) compared with 135 +/- 3 mm Hg (CCaDiet); by 12.7 weeks of age, BP was 192 +/- 4 mm Hg (HCaDiet) compared with 233 +/- 3 mm Hg (CCaDiet). Similar results were observed in age-matched SHRs fed the HCaPLDiet. The results show that subcutaneous infusion of ALDO (1.0 microgram/d, osmotic pumps) for 2 weeks to young ADX male SHRs raised on the CCaDiet caused a significant increase in systolic BP when compared with SHRs implanted with Sham pumps (P less than 0.001). High BP associated with ALDO infusion was attenuated by the HCaDiet (BP after 2 weeks was 138 +/- 8 mm Hg for the HCaDiet group compared with 200 +/- 5 mm Hg for the CCaDiet group, P less than 0.001; n = 4 to 6). The results show that the HCaDiet blunts the development of high BP in intact SHRs and may protect against the development of ALDO hypertension in ADX young SHRs.

Effect of high calcium diet and nitrendipine on the development of high blood pressure in adrenalectomised spontaneously hypertensive rats treated with aldosterone.

The present investigation was designed to study the effect of high calcium diet and nitrendipine on aldosterone-induced development of high blood pressure in young adrenalectomised spontaneously hypertensive rats (SHR). Animals raised on a control calcium diet (0.5% Ca) or high calcium diet (2.5% Ca) were adrenalectomised aged 5-6 weeks and treated with either aldosterone (1 microgram/day subcutaneously) in propylene glycol or aldosterone (1 microgram/day) plus nitrendipine (20 mg/kg/48 hr subcutaneously) in peanut oil. Controls received the aldosterone or nitrendipine vehicle and treatment lasted two weeks. The animals were given 0.9% NaCl ad libitum. Aldosterone caused a significant increase in systolic BP in adrenalectomised SHR fed the control calcium diet when compared with controls and the aldosterone-induced hypertension was blocked by the high calcium diet and nitrendipine (P less than 0.001, n = 4-7). These findings suggest that high dietary calcium has a protective effect against the development of aldosterone-induced hypertension and may enhance that of nitrendipine.

Modulation of adrenergic neurotransmission in the rat tail artery by dietary lipids.

The effects of dietary lipids on prejunctional alpha 2-adrenoceptor function were investigated in perfused/superfused caudal arteries from adult rats. The investigation was designed to study the effects of diet supplemented with saturated fatty acids (coconut oil diet) or unsaturated fatty acids (sunflower oil diet) on alpha 2-adrenoceptor neuronal function in the proximal rat tail artery. Pregnant rats were fed Purina Rodent Chow (reference diet) or a semisynthetic diet containing 16% (wt/wt) of either sunflower oil or coconut oil. Neonatal pups were exposed to the diet via maternal milk and weaned rats were maintained on the same diet throughout adulthood. Artery segments (5-6 cm) were prelabeled with [3H]norepinephrine and perfused/superfused with Krebs-bicarbonate solution at 37 degrees C. The release of endogenous norepinephrine, total 3H, and [3H]norepinephrine was measured during field stimulation (supramaximal voltage, 5 Hz, 1 ms duration, for a total of 1,200 pulses). Both test diets caused a significant increase in norepinephrine content when compared with the reference diet (p less than 0.01). The results show that field stimulation-evoked release of norepinephrine from arteries obtained from rats fed coconut oil diet was significantly less than that exhibited by either the sunflower oil group or the reference group (p less than 0.05). Phentolamine (3 microM) caused a significant increase in percent release of endogenous norepinephrine and total 3H (p less than 0.05) in all groups. However, the increase above control values for the sunflower oil group was higher than the coconut oil group which suggested that dietary manipulations altered alpha2-adrenoceptor sensitivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of etorphine on adrenergic neurotransmission in the rat and guinea pig heart.

The effect of etorphine (ET) on nerve stimulation-mediated release of norepinephrine (NE) was investigated in isolated rat and guinea pig hearts. Hearts were perfused with Krebs bicarbonate solution via the aorta and the overflow of NE was measured after stimulation of the heart. ET (0.001-0.1 mumol/l) caused a dose-dependent inhibition of NE release in both preparations. Inhibition of NE release from guinea pig hearts ranged from 13% at 0.001 mumol/l to 24% at 0.1 mumol/l. The same concentrations of ET decreased NE release by 10 and 36% in the rat heart. The inhibitory effect of ET was blocked by naloxone. It is concluded that presynaptic opioid receptors located on the adrenergic neuronal terminals may be involved in the regulation of adrenergic neurotransmission in the rat and guinea pig heart.

Effect of dietary lipids on myocardial norepinephrine content and field stimulation-mediated release of norepinephrine from perfused neonatal and adult rat hearts.

The effects of dietary lipids on the content and release of norepinephrine and on the overflow of norepinephrine after alpha-adrenoceptor blockade with phentolamine were investigated in isolated perfused rat hearts. Pregnant rats were fed Purina Rodent Chow (reference diet) or a semisynthetic diet containing 16% (wt/wt) of either coconut oil (saturated fatty acids) or sunflower oil (unsaturated fatty acids). Neonatal pups were exposed to the diet via maternal milk and weaned rats were maintained on the same dietary lipid supplementation. Coconut oil caused a significant decrease in cardiac norepinephrine in all age groups when compared with the reference diet (p less than 0.01). Sunflower oil caused a significant increase in cardiac norepinephrine at 14 and 21 days of age when compared with coconut oil (p less than 0.05). Hearts prelabeled with [3H]norepinephrine were stimulated with supramaximal voltage (5 Hz, 2 ms duration, 300 pulses). At 14 and 21 days, coconut oil caused a significant decrease in norepinephrine release when compared with sunflower oil (p less than 0.05). The release of norepinephrine from hearts exposed to sunflower oil diet and the reference diet were comparable. These alterations in neuronal storage and exocytotic release of norepinephrine may be due to dietary-induced membrane perturbations. Phentolamine (10(-8)-10(-6) M) caused a dose-related increase in norepinephrine release following stimulation (supramaximal voltage 2.5 Hz, 150 pulses) of adult rat hearts from all dietary groups. However, the increase above control values was highest for coconut oil and lowest for sunflower oil (p less than 0.01), suggesting changes in receptor sensitivity. It appears that dietary lipid supplementation in the developing and adult rat could affect the myocardial alpha-adrenoceptor microenvironment which could cause changes in the prejunctional alpha-adrenoceptor neuronal function.

Papillary muscle dynamics: in situ function and responses of the papillary muscle.

Experiments were designed to 1) study in situ changes in papillary muscle length and force during the cardiac cycle, 2) investigate the relationship between papillary muscle length and maximal ventricular pressure, 3) study the effect of both positive and negative inotropic intervention on this relationship. A mercury gauge transduceror Walton-Brodie strain-gauge arch was sutured to the anterior papillary muscleand used to measure the extent of shortening or lengthening (deltaL) or force (APMF),.respectively. The anterior papillary muscle showed rapid increase of length and forcewhile contracting during isovolumic contraction and reached peak systolic length at end-isovolumic contraction or during the early injection phase. The papillary muscle was observed to shorten during the phases of ejection and isovolumic relaxation. It was concluded that changes in ventricular pressure during the cardiac cycle are associated with changes in papillary muscle length and force such that the resulting "lengthening contraction force" is appropiate for maintenance of normal atrioventricular valve function during isovolumic contraction. There was an inverse relationship between deltaL and maximal ventricular pressure such that for each increment in peak ventricular pressure there was a decrease in deltaL. The deltaL-force relationship was shifted upward and to the right by norepinephrine (NE) and isoproterenol and downward and to the left by occlusion of the posterior vena cava. Phenylephrine had little or no effect on this relationship.