Study of the rat adrenal renin-angiotensin system at a cellular level.

To address the question as to how zona glomerulosa (ZG) cell angiotensin II (Ang II) secretion is regulated, we developed an immuno-cell blot assay to measure its secretion from single cells. We compared these results with those obtained from population studies using a superfusion system. Modulation of Ang II secretion was investigated acutely (by administrating potassium [K+] or captopril) and chronically (by feeding the animals low or high sodium diets). The area of secretory cells, halo areas, and halo intensities varied widely but were highly significantly correlated (P < 0.001) with each other. A disproportionate amount of Ang II was secreted by a small number of large cells. When K+ concentration was increased from 3.6 to 0 mM, superfused ZG cells increased their Ang II secretion 2.32 +/- 0.59-fold. Administration of captopril reduced the K(+)-stimulated Ang II secretion 1.24 +/- 0.07 fold. These findings were reflected in the cell blot assay as a change in the frequency distribution of halo area by K+ and captopril in the same direction as in the population study. In both conditions, the percentage of secretory cells did not change significantly from control. Superfused ZG cells from rats on a low sodium diet secreted 1.85 +/- 0.58-fold more Ang II than cells from sodium-loaded rats (p < 0.05, n = 6). The cell blot assay confirmed these findings with sodium restriction significantly increasing (P < 0.001) both the halo area and its frequency distribution to a larger portion of high secreting cells. However, in contrast to acute treatment with K+ or captopril, the number of secretory cells also doubled. Thus, the individual ZG cell uses two mechanisms to modify Ang II production. In response to acute stimulation and suppression, the amount of Ang II secreted per cell is modified without changing the number of secretary cells. With chronic stimulation, both the amount of Ang II secreted per cell and the number of secretary cells increase.

The effect of losartan on potassium-stimulated aldosterone secretion in vitro.

Potassium (K+) and angiotensin-II (Ang-II) are two distinct secretagogues for aldosterone release. However, a local adrenal renin-angiotensin system is present, and several studies suggest a complex interaction between K+ and locally produced Ang-II. First, superfusing zona glomerulosa (ZG) cells with K+ stimulates the secretion of both Ang-II and aldosterone. Second, K(+)-stimulated aldosterone secretion can be reduced in the presence of angiotensin-converting enzyme inhibitors. Because angiotensin-converting enzyme inhibitors are not specific inhibitors of the adrenal renin-angiotensin system, we further tested the hypothesis that locally produced Ang-II participates in K(+)-stimulated aldosterone release from rat ZG cells by using a specific Ang-II antagonist. Although type 1 (AT1) and type 2 (AT2) Ang-II receptors are present in ZG cells, only AT1 antagonist has been shown to mediate Ang-II-induced aldosterone secretion. Losartan, a specific AT1 antagonist, was used in this study. In the presence of losartan (10 microM for 9 mM K+ and 100 microM for 5 mM K+), the average aldosterone secretion during 2 h of superfusion with 9 mM K+ and 5 mM K+ was 70.1 +/- 5.4% (n = 5) and 58.5 +/- 2.2% (n = 3), respectively, of that in its absence. Losartan did not alter the amount of Ang-II secreted. The inhibitory effect of losartan lasted longer than 60 min after it was terminated. In summary, our results support the hypothesis that locally produced Ang-II contributes to the aldosterone secretory response to K+ stimulation at both physiological and supraphysiological levels.

Potassium-stimulated angiotensin release from superfused adrenal capsules and enzymatically dispersed cells of the zona glomerulosa.

The cells of the adrenal cortex contain angiotensin-II (AII), but whether this peptide is synthesized there (vs. internalized from the systemic circulation), whether it is secreted, and whether it is important in aldosterone production remain uncertain. To address these issues, we studied AI and AII release from superfused rat adrenal capsules and dispersed glomerulosa cells. Superfused adrenal capsules released 7-fold more AII in 270 min than the capsules originally contained (495 +/- 101 fmol AII/rat released vs. 66 +/- 8 fmol AII/rat tissue content). The amount of AI released in the same period only slightly exceeded the tissue content. In response to higher potassium concentrations in the medium (9 vs. 3.6 mM K+), adrenal capsules and dispersed glomerulosa cells both released significantly more AI and AII into the superfusate. This release of AI and AII was oscillatory. The oscillations occurred in each of 15 experiments, with a period of 45-90 min. Decapsulated adrenal glands (the zona faciculata/reticularis plus medulla) also contained and released AII, but did not respond to potassium stimulation. There was a highly significant correlation between AII and aldosterone release. This was especially apparent if aldosterone secretion was examined during oscillations of AII release (r = 0.97; P less than 0.0001). We conclude that AII is synthesized in the zona glomerulosa and can be released in response to stimuli. The close correlation between AII and aldosterone secretion suggests that locally produced AII may play an important role in aldosterone biosynthesis.

The effect of sodium intake on angiotensin content of the rat adrenal gland.

To determine whether dietary sodium intake modifies the generation of adrenal-produced angiotensins and/or their relative proportions, Sprague-Dawley rats were maintained on a low (0.02%), normal (0.4%), or high (1.5%) sodium intake for 5 days. The animals were then killed by decapitation at 0900 h, and their adrenal glands were removed and dissected into two parts: capsular tissue, containing the zona glomerulosa (ZG), and the decapsulated adrenal gland. The tissue was frozen in liquid nitrogen and extracted, and the individual angiotensins [angiotensin-II (AII), angiotensin-III (AIII), angiotensin-I (AI), and Des-Asp-angiotensin-I (Des-Asp-AI)] were separated by HPLC and quantitated by RIA. On a normal sodium intake, the molar contents of the four angiotensins were similar in ZG, ranging from 3.1-6.6 pmol/g, although AII was present in a 60-70% higher concentration than AIII. In the decapsulated adrenal, the concentrations of the various angiotensins were again similar, but the absolute levels (per g tissue) were significantly (P less than 0.02) less than those in the ZG layer. With sodium restriction, the AII content increased more than 2-fold in the ZG, but not in the decapsulated adrenal tissue. In contrast, both AI and Des-Asp-AI significantly (P less than 0.01) decreased with sodium restriction, so that their contents on the low salt diet were only 15-20% of those observed on the high sodium diet. Thus, there was an inverse correlation (P less than 0.001) between the salt content of rat chow and the AII content of the ZG. The correlation between salt intake and AI as well as Des-Asp-AI levels was direct and significant (P less than 0.02). The AIII level in the ZG was similar on all diets. After a lag period, ZG AII increased sharply between 16-48 h of sodium restriction. These data document that sodium intake has a profound effect on the angiotensin content of the ZG, with sodium restriction substantially increasing the levels of AII while reducing the level of its substrate, AI. This also appears to be unique for glomerulosa cells, as in the decapsulated adrenal gland there is little if any change with sodium restriction. We conclude that these sodium-mediated changes in tissue AII production may be involved in the increased responsiveness of glomerulosa cells to aldosterone secretagogues during sodium restriction.

Chemistry and biological activities of N,N-dimethylaminoethyl acrylate, a choline acetyltransferase inhibitor.

N,N-Dimethylaminoethyl acrylate (acryl-DMA) was synthesized as a tertiary nitrogen choline acetyltransferase (ChAc) inhibitor which would be able to penetrate biological membranes to inhibit ChAc in the nerve terminal. The synthesis from dimethylaminoethanol and acrylyl chloride was described and the hydration with times in an aqueous medium measured by NMR spectroscopy was presented. The autohydrolysis in water was found to be 1.75 x 10(-8) mol/min at pH 7.4 and 5.0 mM concentration. The enzymatic hydrolysis was unaffected by cholinesterases. Acryl-DMA was capable of inhibiting ChAc extracted from rat brain with I50 of 5.02 x 10(-4) M. The inhibition was reversible and displayed uncompetitive kinetics with respect to both substrates, choline and acetyl-CoA. Neither the hydrolysis nor the hydration products of acryl-DMA could inhibit ChAc. Although acryl-DMA was hydrated rapidly and completely within 1 hr at high pH (9.0), the time course of inhibition ability of acryl-DMA in aqueous medium at physiological pH was found to decrease rather slowly and by 36% in 1 hr, indicating that acryl-DMA can survive from hydration at physiological pH. Acryl-DMA was also tested for its ability to block electrically induced muscle contractions in both isolated skeletal and smooth nerve-muscle preparations. The ED50's obtained were less than 5 x 10(-4) M in both cases.

Reduction of intraocular pressure in glaucomatous dogs by a new cholinergic drug.

N-Demethylated carbachol (DMC) was synthesized and analyzed for its ocular effects. DMC has been found to penetrate ocular tissue effectively. It has been shown to be free of acute toxic properties in rabbits and dogs at therapeutic doses and has been demonstrated to lower intraocular pressure of glaucomatous beagles without causing intense miosis. The effects of DMC and pilocarpine on outflow facility were compared in normal dogs. At the dose used in these experiments, both drugs affected outflow facility to a similar extent. It is concluded that DMC could be a potentially useful ocular hypotensive agent.

Studies on the mechanism of action of a new Ca-2+ antagonist, 8-(N,N-diethylamino)octyl 3,4,5-trimethoxybenzoate hydrochloride in smooth and skeletal muscles.

1. The rabbit aortic strip, guinea-pig ileum and rabbit skeletal muscle sarcoplasmic reticulum preparations were used to determine at which sites and in what manner 8-(N,N-diethylamino)-octyl 3,4,5,-trimethoxybenzoate (TMB-8) interferes with Ca2+ availability in smooth and skeletal muscles. 2. TMB-8 (50 muM) significantly inhibited equivalent responses of the rabbit aortic strip to KCl and noradrenaline. 3. TMB-8 (65 muM) produced no significant alteration in the extracellular space of the guinea-pig ileum as measured with [3H]-sorbitol. 4. The resting cellular Ca2+ influx as well as the resting 45Ca2+ efflux in the guinea-pig ileum preparation were significantly inhibited by TMB-8 (65 muM). 5. TMB-8 (5 muM and 50 muM) had no significant effect on the uptake of 45Ca2+ by the sarcoplasmic reticulum preparation of skeletal muscle; however, TMB-8 (5 muM) did significantly inhibit the caffeine (20 mM)-induced release of 45Ca2+ from this preparation. 6. It is concluded that TMB-8 reduces Ca2+ availability in smooth and skeletal muscles by stabilizing Ca2+ binding to cellular Ca2+ stores and thereby inhibits the release of this Ca2+ by contractile stimuli.

Effects of dietary calcium on blood pressure, vascular reactivity and vascular smooth muscle calcium efflux rate in Zucker rats.

Previous data from this laboratory indicate that hypertension in insulin resistant Zucker obese rats is accompanied by an impairment in vascular smooth muscle Ca2+ efflux. Since insulin resistant states are also generally salt-sensitive and dietary Ca2+ reduces blood pressure in some salt-sensitive states, we evaluated the effects of dietary Ca2+ on blood pressure and vascular reactivity and examined whether these effects are due to increased vascular smooth muscle Ca2+ efflux. We assigned 16 obese and 16 lean rats to a normal (0.5%) or high (1.5%) Ca2+ diet for 28 days, following which intraarterial blood pressure and in vitro vascular smooth muscle 45Ca efflux and vascular reactivity responses to phenylephrine and serotonin were measured. Blood pressure was elevated in the obese rats on both diets (P less than 0.2), and the high calcium diet lowered both systolic and diastolic pressure in both the lean and obese rats (P less than 0.5). Vascular reactivity was higher in the obese rats (P less than 0.2), but dietary Ca2+ exerted opposite effects on vascular reactivity to the agonists. High Ca2+ reduced sensitivity to serotonin in the obese rats by 54% (P less than .05) without affecting sensitivity in the lean rats. In contrast, the high Ca2+ diet increased sensitivity to phenylephrine by 31% in both groups (P less than .01). 45Ca efflux was lower in the obese rats compared to the lean rats (P less than .05), and the high Ca2+ diet increased this rate by 23% in the lean, but not the obese, rats (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

On GABA function and physiology in the pineal gland.

Pineal gamma-aminobutyric acid (GABA) content and glutamic acid decarboxylase (GAD) activity were found not to be influenced by environmental light, catecholamines, sympathetic innervation, or input via the pineal stalk. The observation that GAD activity did not disappear after pineal stalk section, ganglionectomy, or 48 h of organ culture leads us to suggest that GAD activity is not located in nerve processes entering the pineal gland. Treatment in organ culture with an inhibitor of protein synthesis did not greatly influence the slow rate of decrease of GAD activity. This finding is consistent with the conclusion that GAD turnover is slow. Treatment of denervated glands or glands containing functional sympathetic nerve structures with GABA, amino-oxyacetic acid (AOAA) or bicuculline in organ culture did not alter unstimulated levels, or significantly block the adrenergic stimulation of the activity of pineal serotonin N-acetyl transferase (NAT). It is clear from our studies that GABA does not influence or modulate the adrenergic regulation of.pineal NAT activity, and that GABA content and synthesis are not regulated by an adrenergic mechanism. The role of GABA in the pineal gland remains to be discovered.

In vivo effects of some tertiary alkylaminoethyl esters with choline acetyltransferase inhibitory properties.

The tertiary nitrogen derivatives of two choline esters, chloroacetylcholine and acrylcholine, known to inhibit choline acetyltransferase (ChAc) in vitro, were tested for their effects in the whole animal, including peripheral and central cholinergic systems. These esters are N,N-dimethylaminoethyl chloroacetate (Cl-DMA) and N,N-dimethylaminoethyl acrylate (acryl-DMA). The peripheral preparations studied included a neuromuscular junction, a sympathetic ganglion and a postganglionic parasympathetic exocrine preparation. Both Cl-DMA and acryl-DMA blocked responses in these preparations when injected intravenously. The LD50 values for Cl-DMA and acryl-DMA were 640 mg/kg and 183 mg/kg, respectively. Cl-DMA and acryl-DMA were also able to inhibit brain ChAc when injected intravenously by 32% and 18.5%, respectively. The brain levels of acetylcholine (ACh) were significantly reduced by about 25% with Cl-DMA but not significantly with acryl-DMA when the animals were forced to exercise after injection. It is obvious that ChAc inhibition is not effective in decreasing ACh levels significantly under normal conditions.

Effects of diethylcholine in two animal models of Parkinsonism tremors.

(2-Hydroxyethyl) methyldiethylammonium iodide (diethylcholine; DEC) was tested against trihexyphenidyl for its ability to block tremors in two animal models of Parkinsonism tremors. Both DEC (75 mg/kg) and trihexyphenidyl (10 mg/kg) antagonized physostigmine tremors in mice. Both drugs also blocked tremors in rats which received intracaudate injections of carbachol. DEC was more efficacious than trihexyphenidyl in the rat model. No dose-related inhibition of tremors was seen for trihexyphenidyl (5--20 mg/kg) but inhibition by DEC was dose-related (25--50 mg/kg). The ED50 for tremor inhibition in the rat model by DEC was 33 mg/kg. DEC was also shown to cross the blood-brain barrier in mice. The probable mechanism of action of DEC is discussed.

Cytolysis of neuroblastoma cells in vitro and treatment of neuronal tumors in vivo with bromoacetylcholine.

The effect of bromoacetylcholine on mouse neuroblastoma C-1300 was investigated in cell culture as well as in A/J mice. In vitro, bromoacetylcholine (1 X 10(-5) M) was a potent cytolytic agent and produced an additive effect in combination with vincristine (3 X 10(-9) M). Since the choline acetyltransferase inhibitor, dimethylaminoethyl chloroacetate, does not inhibit neuroblastoma efficiently in vitro, the potent cytolytic action of bromoacetylcholine is probably not due to its choline acetyltransferase inhibitory action. Furthermore, the neuroblastoma inhibitory effect of bromoacetylcholine was not affected by atropine. Therefore, the inhibitory action is not related to the interaction of bromoacetylcholine with muscarinic receptors either. In in vivo experiments, 1, 10, or 30 mg/kg of bromoacetylcholine was injected directly into the tumors three times daily for 6 weeks. Bromoacetylcholine at 10 and 30 mg/kg gave significant protection of A/J mice from the death induced by neuroblastoma inoculation, and the lifespan was prolonged significantly with these bromoacetylcholine treatments.

Treatment of neuroblastoma in mice with bromoacetylcholine and bromoacetate.

Bromoacetylcholine (30 mg/kg intratumor one to three times per day) and bromoacetate (12 mg/kg intratumor two times per day) inhibited neuroblastoma in A/J mice efficiently and prolonged the lifespan of these animals at least 200%. Since the neuroblastoma-inoculated A/J mice are considered to be comparable to human neuroblastoma, the cytolytic action of bromoacetylcholine and bromoacetate on murine neuroblastoma warrants further studies on patients. The fact that these tumors were cured in adult mice is very important because older children and adults with neuroblastoma have the poorest prognosis.

Pharmacological studies on N-demethylated carbachol.

In attempts to find a drug more active than pilocarpine, the tertiary nitrogen derivative of carbachol, N-demethylated carbachol, was synthetized and tested on several autonomic nervous system preparations. N-Demethylated carbachol was active at muscarinic and nicotinic sites in vivo and in vitro. In superfusion studies, N-demethylated carbachol contracted the smooth muscle of the guinea pig ileum as well as skeletal muscles of frog recus abdominis and chick biventer cervicis. N-Demethylated carbachol decreased blood pressure in the rat, with an ED50 ("/- SEM) of 4.82 +/- 0.78 mg/kg. After close arterial injection to the cat superior cervical ganglion, N-demethylated carbachol elicited contractions of the nictitating membrane (ED50 of 1.68 +/- 0.24 mg/kg) that were not significantly affected by atropine. N-D-methylated carbachol stimulated salivation in dog Wharton duct preparations with an ED50 of 2.55 +/- 0.81 mg/kg. In contrast, pilocarpine had no effects on skeletal muscles in vitro, produced ganglionic effects blocked by atropine, had a prominent effect on salivation, and tended to elevate blood pressure.

Therapeutic embolization of post-cholecystectomy hepatic artery aneurysm.

A "sandwich" technique employing steel coils and gelfoam embolization was applied in two cases of hepatic artery aneurysms. Immediate cessation of the bleeding was evident clinically and the post-embolization angiogram showed occlusion of the vascular lesion. Cholecystectomy is one of the most common abdominal operations and it is generally well tolerated, particularly in young and middle-aged patients. Morbidity rates of 5% to 32% and mortality rates of 0.4% to 2.5% have been reported, depending on such factors as age, underlying illness, etc. (1-4). The most frequent complications of cholecystectomy are wound infection, abscess, ductal injury or ligation, and bleeding. This paper describes two cases of hepatic pseudoaneurysm following iatrogenic damage during cholecystectomy which was treated with transarterial embolization.