Anthony D. Okonmah

Effect of Ciclosporin on Rat Liver and Kidney Glutathione Content

The effect of ciclosporin (CS) on hepatic and renal glutathione was investigated in 36 male Sprague-Dawley rats weighing 200-250 g each. CS (120 micrograms/kg/day, i.p.) treatment caused a significant decrease in both hepatic and renal glutathione content. The rat hepatic glutathione levels decreased by 16% within 1 h of a single CS treatment and continued decreasing to 50% following chronic treatment with CS for 7 days. Renal glutathione content decreased only marginally (3%) within 1 h of CS treatment. However, it decreased by 17% within 24 h and continued to decrease during the 7 days of chronic treatment. This decrease in the content of both hepatic and renal glutathione may contribute to the toxicity observed during treatment with CS.

Circadian variation in the acetylcholinesterase activity of specific rat brain areas

Abstract Acetylcholinesterase (AChE) activity of the adenohypophysis, cerebellum, cerebral cortex, hypothalamus, amygdala, hippocampus, midbrain, pons, medulla oblongata and caudate nucleus was determined by a spectro‐photometric method in adult, male rats adapted toan LD 12:12cycle. Results of the study show that AChE activity is highest during the light phase and lowest during the dark phase of the cycle in all the brain areas studied except the adenohypophysis, cerebellum, hippocampus and hypothalamus. These findings expand earlier observations on the circadian variation in rat brain AChE activity and suggests a relationship with reported circadian variation in the acetylcholine levels of rat brain.

Effect of cyclosporin A on rat kidney catecholamines

The immunosuppressive agent, Cyclosporin A, (CsA) has been associated with nephrotoxicity and hypertension. The mechanism for these effects are not known. We therefore determined the levels of the catecholamines; epinephrine (EPI), norepinephrine (NE) and dopamine (DA) and some of their metabolites; epinine, dihydroxyphenyl-acetic acid (DOPAC), homovanillic acid (HVA), metanephrine (ME) and 3-methoxy-4-hydroxy-phenylglycol (MHPG) in the kidneys of rats treated intraperitoneally with either CsA (120 micrograms/kg/body wt/day) or control vehicle (1 ml olive oil/kg body wt/day). Six control or CsA treated rats were sacrificed at 1 hour or 24 hours after a single treatment or after 7 days of daily treatment. Renal catecholamine levels were determined using HPLC-amperometric detector. Treatment with CsA increased renal NE and EPI levels by 59% and 70% respectively within 1 hour. In the rats sacrificed 24 hours after treatment, renal NE, EPI and DA levels were similar to or less than the control levels. Treatment with CsA for 7 days resulted in marginal increases in renal NE (22%) and EPI (30%). These changes were associated with a significant decrease in the levels of catecholamine metabolites in the CsA treated kidneys as compared to the controls. The above findings suggest that increases in renal catecholamines may be involved in the CsA-induced hypertension and nephrotoxicity, perhaps by increasing renovascular resistance.

The effect of neuroleptic drugs on serum testosterone level in the male rat

The effects of systemically administered haloperidol (haldol) and N-ethoxycarbonyl-2-ethoxy-1,2, dihydroquinoline (EEDQ) on serum testosterone level were studied in Sprague-Dawley adult male rats. Animals were injected intraperitoneally with either 0.1, 5 and 10 mg/kg of haldol or 0.5 and 5 mg/kg of EEDQ. Animals were sacrificed at 15, 60 min, 12, 24 or 48 hr after drug treatment and blood was collected for subsequent testosterone analysis. Results obtained indicate that 10 mg/kg of haldol significantly (P less than 0.01) suppressed serum testosterone levels both at 1 and 24 hr post drug treatment. EEDQ treatment significantly (P less than 0.01) suppressed serum testosterone levels only when administered at the higher dose of 5 mg/kg. This effect was observed as long as 12 hr after drug treatment. These results suggest that high doses of haldol and EEDQ can suppress serum testosterone levels in the male rat. The sexual dysfunction associated with neuroleptic drugs may be partially due to the effects of the drugs on serum testosterone levels.

Combination chemotherapy of the epipodophyllotoxin derivatives, Teniposide and Etoposide

SummaryPrevious studies in vitro on the influence of extracellular protein binding of Teniposide (VM26) and Etoposide (VP16-213) on subsequent cellular uptake by experimental murine tumor cells [Cancer Res 38: 2549 (1978); Drug Metab Rev 8: 119 (1978)] suggested that a timed-sequential combination of VM26 and VP16-213 may increase the bioavailability of VP16-213. This was studied clinically in six cancer patients with ascites (five ovarian, one rectal) whereby VM26 (20 mg/m2) was given i.p. 2 h prior to VP16-213 (100 mg/m2; i.p.). In some patients, this regimen was administered i.v. The i.v. regimen was found to be more toxic (myelosuppression, nausea, vomiting) than i.p. regimen at same doses of drugs. Several patients remained stable to disease during 1–2 courses of therapy (3 weeks per course), one patient had partial remission, and has been stable in her disease for more than 4 months.In two patients, plasma and ascites fluid was analyzed for VP16-213 and VM26 by a new reverse-phase high performance liquid chromatography method. Both VM26 and VP16-213 could be eluted isocratically (28% v/v acetonitrile in water) from a c18 column with retention times of 6.6 and 13.3 min, respectively. Subsequent pharmacokinetic analysis of one patient suggests that protein binding displacement of VP16-213 in plasma and perhaps ascites fluid increased the pharmacokinetic volume of distribution (28 l) and reduced the elimination half-life (12 h). The data suggests that VP16-213 is distributed more widely in the body and is represented by a single compartment pharmacokinetic model. Analysis of VM26 in ascites and plasma suggests that the so-called “deep pharmacokinetic compartment” represents ascites equivalent space and that the plasma concentration represents VM26 as free and protein-bound drug in kinetic distinguishable compartments.Determinants of drug action are potentially composed of a multiplicity of physiological, biochemical, and other factors. The potential for manipulating the pharmacodynamic properties of drugs to achieve greater therapeutic potential needs further study.

Influence of Ethanol on Fetal Brain Cholinergic Enzyme Activities

Cultured brain cells from rat fetuses of ethanol-treated mothers demonstrated more than 2-fold elevations in choline acetyltransferase (ChAT) activity relative to those of control (saline-exposed) fetal brain cells. When cells from control animals were incubated in vitro for 5 days with 0.1% ethanol, ChAT activity was found to increase more than 4-fold. Brain cells from in utero ethanol-treated animals further exposed to ethanol in vitro for 5 days demonstrated significantly higher ChAT activity compared to cells exposed to ethanol only in vivo. These levels were more than 6 times greater than those of central nervous system cells never exposed to ethanol. Acetylcholinesterase (AChE) activity was significantly elevated (greater than 4-fold) in fetal brain cells when ethanol was present both in vivo and in vitro, but neither treatment alone resulted in any significant changes in AChE. These effects of ethanol on enzymes involved in acetylcholine metabolism may contribute to the different developmental neurologic abnormalities associated with fetal alcohol exposure.

Alterations of fetal brain biogenic amine metabolites by maternal ethanol exposure

1. Pregnant Sprague-Dawley rats treated chronically with ethanol (3 g/kg daily for the last third of pregnancy) had decreased placental weights at birth (ca 23%). 2. Whole fetal brain levels of HVA and 5-HIAA were similarly decreased 32 and 38%, respectively. 3. MHPG levels were also marginally reduced (i.e. 15% decline). 4. In the presence of a potent type A MAO inhibitor (harmaline, 10 mg/kg maternal weight 2 hr before fetal delivery) co-treatment with ethanol was found to result in a 60% elevation of whole fetal brain norepinephrine levels. 5. Other biogenic amines and metabolites were not altered by ethanol treatment.

Corticosteroid effects on cholinergic enzymes in ethanol-treated fetal brain cell cultures

In the presence of ethanol, corticosterone and dexamethasone inhibit choline acetyltransferase and acetylcholinesterase activities in cultured fetal brain cells of the rat. These results suggest that corticosteroids may have an important influence on the activity of cholinergic enzymes in the fetal brain and may antagonize the effects of ethanol in this setting.

Effect of cyclosporin A on the content of glutathione in the brain of the rat

The effect of cyclosporin A on the content of glutathione was investigated in various regions of the brain of male Sprague-Dawley rats, weighing 275-300 g each. Treatment of rats with cyclosporin A (120 micrograms/kg/day, i.p.) resulted in approximately 50% decrease in the content of glutathione of the cerebellum within 1 hr, relative to time-matched controls, treated with olive oil vehicle. During the same period, cyclosporin A also caused an apparent, but statistically insignificant, decrease in the content of glutathione of the hypothalamus (37%), pontine nucleus (37%) and medulla oblongata (10%) and had no apparent effect on that of the cerebral cortex and the caudate nucleus. Within 24 hr of a single treatment, the content of glutathione of the rats treated with cyclosporin A returned to the control concentrations in all the regions of the brain. After 7 days of daily treatment with cyclosporin A, the content of glutathione of the hypothalamus remained within control levels, whereas that of the pontine nucleus showed an apparent decrease (30%) and those of the medulla oblongata and cerebellum decreased significantly, again by 58% and 64%, respectively, relative to their controls. This selective depletion of the content of glutathione in brain may contribute to some of the neurological side effects of cyclosporin A.

Pentylenetetrazol Effect on Adrenocortical Maturation in the Rat

The effect of pentylenetetrazol on adrenal cortex maturation was investigated. Two different groups of weanling Sprague-Dawley female rats were used. At the ages of 23 and 29 days, the animals were treated with pentylenetetrazol (10 mg/kg) for 3 days. Results indicated that pentylenetetrazol decreased plasma corticosterone levels of both age groups. This treatment abolished the corticosterone diurnal variation of the 23-day-old rats, but not that of the 29-day-old rats. An increase in uterine weight was also observed in the pentylenetetrazol-treated animals. Results from this study suggest that CNS stimulation with pentylenetetrazol can alter the adrenal cortex maturation.