L-DOPA biotransformation: correlations of dosage, erythrocyte catechol O-methyltransferase and platelet SULT1A3 activities with metabolic pathways in Parkinsonian patients.

The objectives of this study were to determine (1) the effects of dose and drug absorption on pathways of biotransformation of L-DOPA in Parkinsonian patients treated with Sinemet, and (2) the extent to which genetically-determined variations in the activities of erythrocyte catechol O-methyltransferase and/or platelet phenol sulfotransferase might be reflected in individual differences in L-DOPA metabolism. In the 19 patients studied, there were negative correlations between dosage or absorption and extent of O-methylation and of sulfation of L-DOPA or its metabolites. Levels of activity for erythrocyte COMT were also reflected in individual variation in the metabolism of L-DOPA. In contrast, differences in platelet phenol sulfotransferase were not reflected in differences in sulfation of L-DOPA or of its metabolites. If such a relationship did exist, it might have been obscured by the effects of high dosage of L-DOPA, effects which might have resulted from a deficiency of the sulfation cosubstrate 3'-phosphoadenosine 5'-phosphosulfate in patients taking higher doses of drug.

Adrenomedullary secretion of DOPA, catecholamines, catechol metabolites, and neuropeptides.

Catecholamines and their metabolites have been proposed as markers of sympathetic nervous system stimulation. However, the adrenal medulla is a rich source of catecholamines and catecholamine metabolites and may play a significant role in plasma levels of these compounds. In addition to adrenal catecholamine metabolite efflux, the role of the catecholamine precursor 3,4-dihydroxyphenylalanine (DOPA) has not been fully evaluated. The simultaneous effluxes of catecholamines, metabolites, DOPA, and neuropeptides were measured in perfusates from isolated dog adrenals. The relative abundance of compounds detected consistently during unstimulated conditions was epinephrine >> norepinephrine > 3,4-dihydroxyphenylglycol > metanephrine > normetanephrine > dopamine > 3,4-dihydroxyphenylacetic acid > 3-methoxy-4-hydroxyphenylglycol > or = DOPA >> [Met]enkephalin >> neuropeptide Y. Effluxes of analytes were not affected by cocaine and the ratios of catecholamines to metabolites increased dramatically with carbachol stimulation, consistent with negligible reuptake into adrenal cells. Thus, most of the 3,4-dihydroxyphenylglycol is expected to be derived from epinephrine and norepinephrine subsequent to translocation from chromaffin vesicles into the cytosol. The efflux of DOPA increased dramatically during stimulation with 30 microM carbachol in a calcium-dependent manner. Efflux of DOPA during the initial stabilization period of the perfusion preparation declined exponentially, in parallel with the effluxes of the catecholamines and neuropeptides but not with metabolites. Evoked release of DOPA was Ca2+-dependent. These data suggest that DOPA can be stored and released exocytotically from chromaffin granules.

Antagonists of cyclic nucleotide phosphodiesterase (PDE) isozymes PDE 3 and PDE 4 suppress lymphoblastic response to HLA class II alloantigens: a potential novel approach to preventing allograft rejection?

As a potential novel approach to preventing renal allograft rejection, we investigated whether the proliferative response of lymphocytes to mismatched HLA class II antigens in mixed lymphocytic culture (MLC) can be suppressed by antagonists of cyclic nucleotide phosphodiesterase (PDE) isozymes. Cilostamide, an antagonist of isozyme PDE3 and, to an even greater extent, in combination with rolipram, an antagonist of isozyme PDE4, markedly suppressed (delta = -60%; p < 0.01) the mitogenic proliferative response of lymphocytes in MLC to HLA-DR alloantigens from unrelated donors. These observations suggest that the selective PDE isozyme antagonists might have potential as novel drugs in "signal transduction-targeted" pharmacotherapy of renal transplant rejection.

Neuroendocrine differentiation in prostatic intraepithelial neoplasia and adenocarcinoma.

Neuroendocrine cells are thought to have a regulatory role in prostatic epithelial growth and may be prognostically useful in prostatic adenocarcinoma. To determine the extent of neuroendocrine differentiation in high-grade prostatic intraepithelial neoplasia (PIN), a putative precursor of cancer, we studied the immunohistochemical expression of 10 markers in 26 radical prostatectomy specimens with PIN and adenocarcinoma. Expression was measured as mean percent of positive cases and positive high-power (x40) fields. The highest percentage of cases showed immunoreactivity for serotonin (73%, PIN; 54%, carcinoma), neuron-specific enolase (NSE) (67%, PIN; 46%, carcinoma), chromogranin (62%, PIN; 65%, carcinoma), and human chorionic gonadotropin (hCG) (30%, PIN; 22%, carcinoma); the remaining markers showed immunoreactivity in fewer than 5% of cases (somatostatin, calcitonin, corticotropin) or in no cases (thyrotropin, prolactin, and glucagon). At least one of the markers was present in 88% of cases of PIN and 92% of carcinoma. Non-neoplastic epithelial cells expressed serotonin, NSE, chromogranin, and hCG in every case, and the expression was significantly greater than in PIN and cancer. Stepwise regression analysis revealed the following positive correlations: chromogranin expression in PIN and patient age, NSE expression in cancer and number of lymph node metastases, and hCG expression in cancer and percentage of Gleason pattern 5; serotonin expression in PIN and cancer did not correlate with any of the clinical and pathologic factors. Neuroendocrine differentiation is downregulated in prostatic carcinogenesis, with intermediate levels of expression in PIN compared with normal cells and carcinoma.

Sudden infant death with anomalous origin of the left coronary artery.

Autopsy of a 3-month-old girl, an apparent case of sudden infant death syndrome, revealed anomalous origin of the left coronary artery from the right aortic sinus. Acute angulation of the left coronary artery along the aortic root, as well as a focal intramyocardial course within the ventricular septum, may have contributed to episodic luminal narrowing. Anomalous coronary origins of similar type have been associated with sudden death in children, teenagers, and young adults, but have not necessarily been associated with sudden death in older adults. Somewhat similar malformations have been reported in sudden infant death; two cases involved the left coronary artery and six involved the right.

Nicotinic- and muscarinic-evoked release of canine adrenal catecholamines and peptides.

The tissue content and overflow of norepinephrine (NE), epinephrine (Epi), dopamine (DA), Met-enkephalin (Met-Enk), and neuropeptide Y (NPY) from isolated, retrogradely perfused dog adrenal glands were studied. Under resting conditions, approximately 25% of the overflow of autocoids from the glands was Ca2+ dependent; the cholinergic antagonists hexamethonium and atropine had no effects on basal efflux. Stimulation with the nicotinic agonist 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP; 3 or 50 microM) or with the muscarinic agonist pilocarpine (50 microM or 1 mM) evoked releases of autocoids. These releases were blocked or dramatically reduced by appropriate antagonists or by the removal of Ca2+ from the perfusate. Expressed as percentages of tissue stores, the rank order of overflow of autocoids was E approximately DA much greater than NE during resting conditions, DA much greater than E approximately NE during stimulation with 50 microM DMPP, and DA greater than Epi greater than NE during stimulation with 1 mM pilocarpine. These data are consistent with different mechanisms of release for the catecholamines, perhaps from different cell populations. The data support corelease of peptides and catecholamines, although clear pairing of autocoids could not be confirmed.

MAO and L-dopa treatment of Parkinson's disease.

The aim of this study was to determine whether there were differences in the oxidative deamination of dopamine in patients with Parkinson's disease who demonstrated a long-duration response (LDR) to treatment with dopa and carbidopa and in patients who demonstrated only a short-duration response (SDR) to the drugs. The patients who demonstrated LDR had received dopa and carbidopa for a shorter time (3.4y) than had the SDR patients (9.5y). The concentrations of dopamine and 3-methoxytyramine and their deaminated metabolites 3,4-dihydroxyphenylacetic acid and homovanillic acid were measured in 24-h urine samples collected from patients in both groups. The ratios of homovanillic acid to 3-methoxytyramine and dopamine were greater in SDR than in LDR patients suggesting increased oxidative deamination of dopamine in this group. Increased oxidative deamination could be caused by an increase in MAO activity as Parkinson's disease progresses or by the treatment with L-dopa.

Adrenal vein catecholamines and met-enkephalin during staged hemorrhage and naltrexone administration in cats.

Concurrent levels of catecholamines and met-enkephalin in adrenal vein, femoral vein, and femoral artery were measured under baseline conditions and during staged hemorrhage in halothane (1 MAC)-anesthetized cats (Group II, n = 8) and compared to a nonbled control group (Group I, n = 5). In Group III (n = 14) an i.v. bolus of naltrexone in a range of different dosages (0.01 mg/kg to 10 mg/kg) followed by a continuous infusion was administered prior to induction of hemorrhage. In Group II, the loss of 25% of estimated total blood volume led to a significant decrease (-40 +/- 11 mmHg) in mean arterial blood pressure (MABP) without evoking adrenal stimulation. Hemorrhage to 50% of total blood volume was without a further significant fall in MABP, but led to a significant increase in catecholamine and met-enkephalin levels in the adrenal vein. Naltrexone-treated cats in Group III were not different from Group II in regard to hemodynamic and sympathoadrenal response during staged hemorrhage. We conclude that prophylactic administration of naltrexone has no effect on hemodynamic parameters during staged hemorrhage and that the concurrent adrenal secretion of catecholamines and met-enkephalin is not modulated by actions on opiate receptors in the halothane-anesthetized cat.

Free and conjugated plasma catecholamines, DOPA and 3-O-methyldopa in humans and in various animal species.

The aim of the present study was to determine the extent to which plasma catecholamines are conjugated in different animals compared to man and how widespread is the presence of dihydroxyphenylalanine (DOPA) and 3-methoxy-4-hydroxyphenylalanine (3-OMD) in plasma among the different animal species. Free and conjugated norepinephrine, epinephrine, and dopamine were measured in plasma in humans and in several animal species (dog, rat, Gunn rat, cat, rabbit, guinea pig, African green monkey, young pig, calf, and one American black bear) using HPLC with electrochemical detection. The same technique was used to measure free and conjugated DOPA and 3-OMD in plasma of man, dog, rat, Gunn rat, calf, and American black bear. Human plasma contains the highest concentration of total (free and conjugated) catecholamines (46.1 pmole/ml), while low concentrations (below 15 pmole/ml) were observed in unstressed rats, calves, cats, and young pigs. In man, 95.3% of total plasma catecholamines were conjugated. The extent to which plasma catecholamines were conjugated varied greatly between animal species. The conjugated fraction expressed as percentages of the total catecholamines is lowest in the young pig (4.7%) and highest in the bear (100%). Conjugated dopamine was present in the plasma of all species, varying between 3% of the total catecholamine pool in young pig to 90% in dog. Conjugated norepinephrine was also present in plasma of all species except in unstressed rats with access to food. Conjugated epinephrine was detected only in cat and rat. Free DOPA and 3-OMD were present in plasma of all tested species with especially high levels of 3-OMD being present in dog. Conjugated DOPA and 3-OMD were not consistently found in any species. Our results indicate that man, dog, bear, and African green monkey are particularly good catecholamine conjugators and that young pig, guinea pig, rabbit, and calf are poor conjugators.

Effects of hemorrhage and naloxone on adrenal release of methionine-enkephalin and catecholamines in halothane anesthetized dogs.

Concurrent levels of methionine-enkephalin and catecholamines in adrenal vein, femoral vein and femoral artery were measured under baseline conditions and during graded hemorrhage in halothane anesthetized dogs and compared to a non-bled control group. Naloxone was administered in both groups at the end of the experiment. Normotensive hypovolemia with a remaining blood volume of 76% led to a moderate decrease in mean arterial blood pressure from baseline and a 15- to 20-fold increase in norepinephrine, epinephrine and dopamine, and a 5-fold increase in enkephalin in the adrenal vein. Subsequent induction of hypotensive hypovolemia with a remaining blood volume of 51% resulted in a profound drop in blood pressure and evoked a further increase in the level of catecholamines (40- to 50-fold from baseline) and enkephalin (8-fold from baseline) in the adrenal vein. In the control group only a 3- to 4-fold increase from baseline in adrenal vein hormone levels was observed over time. Naloxone administration at the end of the experiment, led to a 2- to 6-fold further increase in hormones at the 3 collection sites in both groups of dogs. Joint calculation of the partial correlation coefficients for the influence of preceding blood volume and blood pressure, and concurrent blood volume and blood pressure on hormone secretion in the adrenal vein revealed that these variables explained the variation in hormone levels between 56 and 92% during normotensive hypovolemia and 62-83% during hypotensive hypovolemia. In one dog with bilateral adrenalectomy, hemorrhage was poorly tolerated, and naloxone administration did not lead to increased systemic plasma levels of catecholamines and enkephalin or improved hemodynamics. In the hemorrhage group, molar ratios of norepinephrine/epinephrine in the adrenal vein showed a significant increasing trend during the experiment. Findings in these experiments support the idea of differential monoaminergic and enkephalinergic regulation in adrenal medullary cells.