Epigenetics and transgenerational transfer: a physiological perspective.

Epigenetics, the transgenerational transfer of phenotypic characters without modification of gene sequence, is a burgeoning area of study in many disciplines of biology. However, the potential impact of this phenomenon on the physiology of animals is not yet broadly appreciated, in part because the phenomenon of epigenetics is not typically part of the design of physiological investigations. Still enigmatic and somewhat ill defined is the relationship between the overarching concept of epigenetics and interesting transgenerational phenomena (e.g. 'maternal/parental effects') that alter the physiological phenotype of subsequent generations. The lingering effect on subsequent generations of an initial environmental disturbance in parent animals can be profound, with genes continuing to be variously silenced or expressed without an associated change in gene sequence for many generations. Known epigenetic mechanisms involved in this phenomenon include chromatin remodeling (DNA methylation and histone modification), RNA-mediated modifications (non-coding RNA and microRNA), as well as other less well studied mechanisms such as self-sustaining loops and structural inheritance. In this review we: (1) discuss how the concepts of epigenetics and maternal effects both overlap with, and are distinct from, each other; (2) analyze examples of existing animal physiological studies based on these concepts; and (3) offer a construct by which to integrate these concepts into the design of future investigations in animal physiology.

Pharmacology of 5'-esters of 1-beta-D-arabinofuranosylcytosine.

Pharmacological studies of 5'-esters of 1 beta-D-arabinofuranosylcytosine (ara-C) were performed in three species (mouse, pig, and man). In mice, after a single i.p. injection of a suspension of tritiated 1-beta-D-arabinofuranosylcytosine 5'-palmitate (PalmO-ara-C) at a therapeutic dose of 150 mg/kg, 30% of the administered radioactivity was recovered in the urine in 24 hr and 56% was recovered after 7 days. Excretion was less rapid after s.c. administration. ara-C and 1-beta-D-arabino furanosyluracil each accounted for about 50% of the excreted radioactivity, and no PalmO-ara-C was found. Plasma ara-C concentrations of greater than 0.1 microng/ml were detected 24 hr after i.p. administration of PalmO-ara-C (150 mg/kg). Single doses of PalmO-ara-C were effective against L1210 leukemic mice when administered 5 to 7 days before tumor inoculation. In a pig, after i.m. injection of tritiated PalmO-ara-C (60 mg/kg, two sites), only 7% of the administered radioactivity was recovered in the urine over a 1-week period. Similar low rates of excretion were also observed in patients treated i.m. with PalmO-ara-C or 1-beta-D-arabinofuranosylcytosine 5'-benzoate. N ara-C was detected in the plasma, which is consistent with the absence of clinical toxicity or myelosuppression in Phase 1 trials of PalmO-ara-C at doses up to 1500 mg/sq m every 3 weeks for as many as eight courses.

Synergistic lethal effect of cis-dichlorodiammineplatinum and 1-beta-D-arabinofuranosylcytosine.

cis-Dichlorodiammineplatinum(II) and 1-beta-D-arabinofuranosylcytosine display a dramatic synergistic effect when tested in simultaneous combination on LoVo cells, a human colon carcinoma cell line. 1-beta-D-Arabinofuranosylcytosine alone does not induce any cytotoxicity on LoVo cells even at high concentrations but is able to increase up to 1000 times the lethal effects of cis-dichlorodiammineplatinum(II). DNA elution experiments show that 1-beta-D-arabinofuranosylcytosine increases the amount of cis-dichlorodiammineplatinum(II)-induced DNA cross-links. The possible mechanisms of this effect are discussed, and some explanations are proposed.

Normocalcemic effect of gallium nitrate in a hypercalcemic rat model.

An established rat hypercalcemia model was used to study the effects of gallium nitrate on elevated serum calcium levels. Gallium nitrate was administered by i.v. or i.p. injection at daily doses of 0.07-0.45 mmol/kg for 5 days to the hypercalcemic rats beginning 1 day following surgery. A dose-correlated normocalcemic response was observed. Gallium nitrate administered late after the induction of the hypercalcemic state was also effective in reducing serum calcium levels. The p.o. administration, however, even at doses as high as 0.45 mmol/kg, did not reduce serum calcium to normal levels. The values of area under the concentration versus time curve (0-24 h) of gallium in normal rats were comparable after i.v. [49.2 (micrograms/ml)h] or i.p. [57.0 (micrograms/ml)h] injections. In contrast, the p.o. route achieved only 15% bioavailability, which may explain the ineffectiveness of p.o. administered gallium nitrate at that dose level. This study suggests that daily i.v. bolus injections of gallium nitrate for managing hypercalcemia may be potentially as effective as the current regimen of continuous i.v. infusion.

Comparison of 5-fluorouracil pharmacokinetics in patients receiving continuous 5-fluorouracil infusion and oral uracil plus N1-(2'-tetrahydrofuryl)-5-fluorouracil.

Plasma 5-fluorouracil (5-FU) levels were compared in the same patients after approximately equimolar doses (1.9 mmol/ m2/day) of 5-day continuous i.v. infusion of 5-FU (CIFU) and oral administration of a formulation of two combined pharmacological agents, uracil (U) plus N1-(2'-tetrahydrofuryl)-5-fluorouracil (ftorafur or FT), a prodrug of 5-FU. Ten patients received CIFU for 5 days, then, after a week wash-out period, began the 28-day oral UFT regimen, which was given in three daily divided doses. Following 1 h of CIFU, the plasma 5-FU levels reached a steady state of 0.6+/-0.2 microM (mean+/-SD; day 1), which was maintained for the entire 5-day infusion period (0.6+/-0.1 microM). In contrast, the maximum 5-FU concentrations (Cpmax) generated from oral UFT at 1 h after dose administration on days 1 and 5 were 2.1+/-1.5 microM and 2.3+/-1.9 microM, respectively, which were higher than the steady-state levels during CIFU. These high 5-FU levels disappeared with an apparent elimination half-life (tl/2,beta) of 5.2+/-2.4 h (day 1) and 7.2+/-3.9 h (day 5). On day 1 of both regimens, CIFU patients had significantly larger 5-FU area under the concentration versus time curve (AUC0-8h) values (4.4+/-1.3 microM.h) than the AUC value when they received the UFT regimen (2.6+/-1.7 microM.h; P = 0.02). However, by day 5, there were no significant differences between AUC0-8 h values in patients receiving CIFU and UFT, respectively (4.8+/-1.5 microM.h versus 3.8+/-2.2 microM.h; P = 0.30)]. On day 5, the average concentration of the metabolite 5-FU at steady-state (Css,aver) within dose interval of 8 h (0.48+/-0.28 microM) for the oral UFT treatment is comparable with the Cpss values of 5-FU from CIFU-treated patients. The post-UFT generated 5-FU pharmacokinetic parameters (higher Cp(mx, comparable Css,aver, equal AUC values, and longer apparent t1/2,beta of 5-FU) may make oral UFT a preferred method of delivering this fluoropyrimidine over CIFU. In addition, oral UFT would eliminate the incidence of venous thrombosis and catheter-related infections sometimes seen in patients treated with CIFU. Furthermore, the convenience and decreased cost of oral administration may be preferable for many patients, particularly those receiving 5-FU for palliation.

Neuronal expression and intracellular localization of presenilins in normal and Alzheimer disease brains.

The expression patterns of presenilin 1 (PS1) and presenilin 2 (PS2) in human normal and Alzheimer disease (AD) brains were investigated using antibodies to specific N-terminal peptides of PS1 (Alzh14A and Alzh14B) and PS2 (Alzh1A-AB). The antibodies to peptides Alzh14A (Alzh14A-AB) and Alzh14B (Alzh14B-AB) detected the full-length protein (approximately 63 kDa) and the N-terminal-processed fragment (36 kDa) of PS1, while the Alzh1A-AB detected mainly the N-terminal-processed fragment (36 kDa) of PS2. Immunofluorescent staining detected by confocal microscopy suggested that both native PS1 and PS2 are localized mainly in the Golgi/ER apparatus. Immunohistochemical studies of human temporal lobes from 2 normal and 5 sporadic Alzheimer brains revealed high levels of PS1 and PS2 expression in the granule cell layer and pyramidal neurons of the hippocampus. Strong immunoreactivity was found in reactive astrocytes and neurofibrillary tangles of all 5 Alzheimer brains. In contrast, only 2 sporadic Alzheimer brains showed presenilin-positive neuritic plaques. These observations suggest that presenilins may be involved in the pathology of some cases of sporadic AD.

Clinical pharmacology of timentin (ticarcillin and clavulanic acid).

Ticarcillin (4 gm) and clavulanic acid (0.1 gm) were simultaneously administered as timentin to patients with cancer as therapy for infections. The pharmacokinetics of both ticarcillin and clavulanic acid were studied in 15 patients after 30-minute and 2-hour intravenous infusions. The mean (+/- SD) ticarcillin plasma peak concentrations after the two infusions were 341 +/- 76 and 210 +/- 60 micrograms/ml. The plasma terminal t1/2 values of ticarcillin were 80 +/- 32 and 56 +/- 12 minutes. The AUCs were 631 +/- 189 and 601 +/- 230 mg/L X hr. The volumes of distribution of the area were 15 +/- 5 and 21 +/- 7 L and total clearances were 115 +/- 36 and 127 +/- 54 ml/min. The corresponding values for clavulanic acid after the infusions are as follows: mean peak concentrations, 5 +/- 1 and 4 +/- 1 micrograms/ml; plasma terminal t1/2 values, 84 +/- 24 and 74 +/- 36 minutes; AUCs, 11 +/- 3 and 11 +/- 6 mg/L X hr; volumes of distribution of the area, 22 +/- 3 and 32 +/- 6 L; and total clearances, 170 +/- 58 and 175 +/- 68 ml/min.

Pharmacologic studies of continuous infusion of arabinosylcytosine by liquid infusion system.

Arabinosylcytosine (ara-C) was administered by prolonged intravenous infusion with a portable liquid infusion system (LIS) to patients with acute myelogenous leukemia. With the use of tritiated ara-C and this portable system, pharmacologic studies were performed in 8 patients. Most of the plasma radioactivity is in the deaminated product, arabinosyluracil (ara-U). After continuous intravenous infusion, a constant ara-C level is achieved slowly in the plasma. Unless a loading (priming) dose is administered immediately before beginning the infusion, a steady-state ara-C level cannot be achieved until 8 to 24 hr after the infusion. The infusion system has two mechanisms--one for giving a loading dose (3 ml/min) and the other for regular infusion at a rate of 0.5 to 2.0 ml/hr. If a loading dose is given before continuous infusion, a steady-state are-C level is achieved within an hour. The plasma ara-C disappearance curves are biphasic with a terminal half-life of 104 min, which is the same as that of a single injection. The cumulative urinary excretion after approximately 23 hr of infusion varied from 14% to 35% in different patients; more than 90% is ara-U and the remainder is ara-C. Our results have demonstrated that LIS can be used conveniently to sustain a constant plasma level of ara-C. The LIS increases mobility of both inpatients and outpatients and is particularly convenient for ambulatory patients.

Clinical pharmacology of trimetrexate.

The clinical pharmacokinetics of trimetrexate were determined in 11 patients during the phase I trial. The plasma drug disappearance curve was triphasic, with a t1/2 alpha of 8 +/- 5 minutes, t1/2 beta of 102 +/- 48 minutes, and t1/2 gamma of 15.2 +/- 5.7 hours. The AUC was 373 +/- 336 (micrograms/ml) hr (normalized to a dose of 200 mg/m2), volume of distribution by the area method (Varea) was 25.2 +/- 16.1 L/m2, total clearance (CL) was 14 +/- 8 ml/min/m2, and renal clearance (CLR) was 8 +/- 6 ml/min/m2. Four patients who received 190 to 200 mg/m2 did not develop severe toxicity. However, three patients who received 120 to 210 mg/m2 developed severe myelosuppression, skin rash, and stomatitis. This latter group had significantly longer terminal half-lives, greater AUCs, smaller Vareas, and lower rates of CL and CLR. One of these patients received an unusually large total amount of trimetrexate (470 mg) because of his obesity. The remaining two patients had renal problems. One developed toxicity despite having received a reduced dose (120 mg/m2) because of impaired renal function. The other patient, with normal renal function, had ascites and had undergone a unilateral nephrectomy for renal carcinoma. These data suggest that prolonged exposure to high trimetrexate levels may lead to increased toxicity. Dosage adjustment may have to be considered for patients who have renal dysfunction.

Ceforanide kinetics.

Pharmacologic studies of the semisynthetic cephalosporin ceforanide were conducted in 29 cancer patients. Intravenous doses of 500 mg over 30 min every 6 hr to 10 patients induced mean peak serum concentrations between 44.7 and 51.5 micrograms/ml, while in 10 patients receiving 1 gm over 30 min every 12 hr mean peak serum concentrations varied from 73.4 to 91.8 micrograms/ml. Twelve hours after 1 gm of drug, mean serum concentrations varied between 5.6 and 6.5 micrograms/ml. After a 500-mg loading dose, continuous infusion of 500 mg every 4 hr, 10 patients maintained serum concentrations above 34.2 micrograms/ml for 7 or 8 days. Most of the drug was excreted in the urine in the initial 6 hr after administration and mean urinary concentration of 1,315 micrograms/ml were obtained during this time. Serum half-life ranged between 2.2 and 2.9 hr on all schedules and therefore wa longer than that of other cephalosporins. No serious toxicity was noted. The relatively broad spectrum of activity in addition to the long half-life suggests clinical utility for this drug.

Radioimmunoassay for etoposide and teniposide.

A radioimmunoassay for VP-16 or VM-26 was developed by using tritiated ligand and antisera produced from rabbits immunized with succinyl-VP-16 bovine serum albumin conjugates. Separate determinations of VP-16 and its hydroxy acid, a metabolite which cross-reacted with the VP-16 antisera, could be accomplished by extracting samples with chloroform in which the metabolite was insoluble. The assay was reproducible and sensitive. Extracted standard curves were linear from 0.025 to 5 micrograms for VP-16 and 0.1 to 10 micrograms for the hydroxy acid per 0.5 ml assay mixture. Fifty percent inhibition of binding was achieved at 0.066 and 0.55 microgram for VP-16 or VM-26 and the metabolite, respectively. Preliminary disposition studies in mice and dog, and human urinary excretion support the application of the assay in pharmacologic studies.

Survey of antibiotic susceptibility among gram-negative bacilli at a cancer hospital.

A survey was conducted of the susceptibility of gram-negative bacilli to selected broad-spectrum antibiotics. The organisms were isolated from all patient specimens submitted to the routine microbiology laboratory during two three-month periods. Overall, the least resistance was observed against imipenem and ciprofloxacin. Considering all of the gram-negative bacilli, differences in susceptibilities to the other antibiotics (aztreonam, cefoperazone, ceftazidime, piperacillin) were minimal. Significant increases in resistance to some antibiotics occurred during the latter period.

In vitro assessment of sulbactam plus cefoperazone in the treatment of bacteria isolated from cancer patients.

Cefoperazone is a broad-spectrum cephalosporin that has been used extensively to treat infections in cancer patients. A recent survey demonstrated only a 6% resistance to this drug among Gram-negative bacteria. The combination of cefoperazone plus sulbactam was studied in vitro against consecutive isolates causing bacteremia in cancer patients as well as those selected for resistance to cefoperazone. Both a fixed ratio of sulbactam/cefoperazone (2:1 w/w) and selected concentrations of sulbactam (2, 4, 8, and 16 micrograms/ml) were studied. Sulbactam was shown to increase the susceptibility of various unselected Gram-negative bacilli; this effect increased with larger concentrations of sulbactam. The addition of sulbactam at optimum concentration levels made 29 of 65 cefoperazone-resistant Gram-negative bacilli susceptible. This effect was seen most markedly for Acinetobacter spp.

Clinical pharmacology of intramuscularly administered L-asparaginase.

Clinical pharmacology of L-asparaginase was compared by intramuscular and intravenous injections in 12 patients with metastatic cancer or leukemia. Following a single intramuscular injection at the gluteal site of L-asparaginase (10,000 IU/m2), the enzyme appeared in plasma as measured initially at 1 hour, but plateau levels were not reached in plasma until 14 to 24 hours after drug administration. The peak plasma level was 1.12 IU/ml, only one fourth of that seen when L-asparaginase was given intravenously at equal doses. However, the enzyme level decrease in the plasma after intramuscular injections was slower, with a half-life ot 46 hours, compared to 7 to 28 hours for intravenously administered drug. The apparent volume of distribution indicated that the intravenously injected enzyme was mostly distributed in plasma, whereas the intramuscularly injected enzyme yielded a much larger volume of distribution (63 versus 245 ml/kg). In addition, only 19 per cent of the intramuscularly injected dose was in plasma, and the area under the curve (C X t) was only 1/24 that by intravenous route (20 versus 487 IU/ml.hr). No enzyme was measurable in patients' urine samples collected for three days after intramuscular injections of the enzyme, and only a trace (less than 1 per cent) of the enzyme was detected in urine after intravenous administration.

A phase I and pharmacokinetic study of oral uracil, ftorafur, and leucovorin in patients with advanced cancer.

A phase I and pharmacokinetics study of oral uracil, ftorafur, and leucovorin was performed in patients with advanced cancer. Uracil plus ftorafur (UFT) was given in a 4:1 molar ratio in three divided doses for 28 consecutive days. Patient cohorts were treated at 200, 250, 300, and 350 mg/m2 of UFT daily. For all patients, 150 mg of leucovorin was given daily in three oral doses. A 1-week rest period followed each 28-day treatment course. Gastrointestinal toxicity, characterized by diarrhea, nausea, and vomiting, was dose-limiting at 350 mg/m2 UFT in patients who had received prior chemotherapy. Mild fatigue and transient hyperbilirubinemia were also common. In previously untreated patients, UFT at 350 mg/m2 was well-tolerated, suggesting this as an acceptable phase II dose in this schedule with leucovorin. Two of eight previously untreated patients with advanced colorectal cancer had partial responses with UFT (350 mg/m2) plus leucovorin. Pharmacokinetic parameters [ftorafur, uracil, 5-fluorouracil (5-FU), 5-methyltetrahydrofolate] showed wide interpatient variations. Plasma levels of 5-FU (Cmax 1.4 +/- 1.9 microM) were comparable to those achieved with protracted venous infusions, and folate levels (Cmax 6.1 +/- 3.6 microM) were sufficient for biochemical modulation. Ongoing study will determine if this convenient oral regimen will compare favorably in terms of efficacy, toxicity, and cost with intravenous fluoropyrimidine programs.

Clinical pharmacology of bruceantin by radioimmunoassay.

During the phase I clinical trial of a new antitumor agent, bruceantin, the pharmacology was studied in 18 cancer patients. The drug was infused intravenously (IV) for 3 h at doses ranging from 1 to 3.6 mg/m2 per day for 5 days. The plasma drug disappearance curves were biphasic, with a fast initial half-life of less than 15 min. The second half-life (t1/2 beta) varied from 0.7 to 38 h among different patients and was not dose-related. The difference between the t1/2 beta on day 1 and that on day 5 was not significant. In patients with normal liver function, the mean plasma concentration at the end of infusion was 22 ng/ml, and the value of the area under the concentration X time curve (AUC) was 111 (ng/ml)h. In contrast, in patients with abnormal liver function the corresponding values were 115 ng/ml and 830 (ng/ml)h, respectively. In addition, these patients had a slower elimination half-life of 10.9 h and a decreased total clearance of 157 ml/min/m2, as compared with 2.6 h and 671 ml/min/m2, respectively, for the normal group. All these differences were statistically significant. Patients with abnormal liver function developed more severe toxicity, including fever, severe nausea, vomiting, and hypotension. Two patients with severe hepatic dysfunction received a reduced dose and developed no toxicity. These results demonstrated the importance of the effects of liver dysfunction on drug disposition and showed that the dosage should be reduced in patients with hepatic dysfunction.

Oral uracil and Ftorafur plus leucovorin: pharmacokinetics and toxicity in patients with metastatic cancer.

PURPOSE: To assess the pharmacokinetics of Ftorafur (tegafur, FT), 5-fluorouracil (5-FU), and uracil in 31 cancer patients who were enrolled in phase I studies of oral uracil and FT (UFT). The correlation between pharmacokinetic parameters and toxic effects of UFT was evaluated. METHODS: Uracil and FT were orally administered in a 4:1 molar ratio at FT doses of 200-400 mg/m2 per day. Patients also received leucovorin at 150 mg/day. Daily doses were divided into three doses and administered at 8-h intervals for 28 consecutive days. Plasma FT concentrations were measured by high-performance liquid chromatography, and plasma 5-FU and uracil concentrations were determined using gas chromatography-mass spectrometry. National Institutes of Health Common Toxicity Criteria were used for assessment of toxicity. RESULTS: The concentrations of FT, 5-FU, and uracil showed wide interpatient variations. Maximum plasma concentrations (Cp(max)) of all three compounds were achieved in 0.3 to 4.0 h. At the various study doses, the terminal half-life (t 1/2beta) of FT ranged from 3.9 to 5.9 h, the area under the concentration-versus-time curve (AUC0-6h) ranged from 16,220 to 52,446 (ng/ml)h, the total clearance (ClT) ranged from 100 to 175 ml/min, and the steady-state volume of distribution (Vd(ss)) ranged from 18.3 to 28.7 l. The 5-FU generated from FT had an apparent distribution half-life (t 1/2alpha) and an apparent elimination half-life (t 1/2beta) of 0.3-1.3 h and 4.9-7.0 h, respectively. The AUC0-6h of 5-FU ranged from 120 to 325 (ng/ml)h. Uracil had a t 1/2alpha of 0.2-0.5 h and the level quickly returned to the endogenous level. The AUC0-6h for uracil ranged from 605 to 3764 (ng/ml)h, the ClT ranged from 3225 to 7748 ml/min, and the Vd(ss) ranged from 341 to 1354 l. The Cp(max) and AUC0-6h of both FT and uracil were significantly correlated with FT doses (P-values of 0.0244 and 0.0112) and with uracil doses (P-values of 0.0346 and 0.0083), respectively. In addition to interpatient variations, intrapatient variations were also observed in six patients who had pharmacology studies done on days 1 and 26+/-2 at the same study dose. We found that the repeated treatment with UFT caused cumulative increases in the values of Cp(max), Ctrough, and AUC0-6h of FT and 5-FU. The major toxic effects observed were diarrhea and nausea and vomiting. The occurrence of these toxic effects correlated significantly with the Cp(max) and AUC0-6h of 5-FU. CONCLUSIONS: The pharmacology studies showed that FT and uracil were readily absorbed orally and that FT was rapidly converted to 5-FU. The preliminary findings suggest that determination of plasma levels of 5-FU after oral administration of UFT may help predict subsequent toxic effects.

L-asparaginase and PEG asparaginase--past, present, and future.

L-asparaginase is an enzyme which hydrolyses asparagine. Since the 1960s it has been known that some leukemic cells are deficient in asparagine synthetase and therefore cannot manufacture sufficient quantities of this essential amino acid to maintain cell viability. L-asparaginase is predominantly useful in acute lymphocytic leukemia (ALL) although responses have been noted in patients with acute myeloid leukemia, lymphoma, and rarely other tumors. L-asparaginase has been used in conjunction with methotrexate and ara-C in combination programs in leukemia. The major side-effect limiting the usefulness of L-asparaginase is allergic reactions. In addition, it is probable that neutralizing antibodies develop which shorten the half life of the drug so that the goal of depletion of plasma levels of asparagine cannot be attained or maintained. Polyethylene glycol (M.W. 5000) can be conjugated to L-asparaginase at sites not involving the active site of the enzyme. This enables free access of a small molecule, asparagine, to the active site of the enzyme but prevents uptake by the reticuloendothelial system, greatly decreasing the probability of developing antibodies against the asparaginase and prolongs the circulating half life of the drug. In a phase I/II study conducted at the M.D. Anderson Cancer Center, 37 heavily pretreated patients with refractory hematologic malignancy were treated. The age range from 15 to 73 years, median 49 years. Nineteen patients had ALL, 15 lymphoma, two myeloma, and one Hodgkin's disease. The dose levels of PEG L-asparaginase varied from 250 IU/m2 up to 8000 IU/m2. The pharmacokinetic profile demonstrated a monophasic half life consistent with a one compartment model with a single elimination phase.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of the effects of cisplatin and N-methyliminodiacetato-(1,2-diaminocyclohexane)-platinum(II) on renal function and gentamicin excretion in rats.

N-methyliminodiacetato(1,2-diaminocyclohexane)-platinum(II) (MIDP) is a new third-generation water-soluble antitumor platinum complex. This study compares the effects of MIDP (3 injections of 25 mg/kg each on days 1, 5 and 9) on renal structure and function and the urinary excretion of gentamicin (GENT) with those of a single 6 mg/kg dose of cisplatin (DDP) in F-344 (Fischer) rats. GENT was given as a single dose of 30 mg/kg 7 days after DDP injection or the last MIDP injection. Rats given DDP and GENT had significantly different plasma urea nitrogen (BUN) levels (315 +/- 79 mg/dl) and creatinine clearance (0.40 +/- 0.24 ml/[min.kg]) than did the control group that was given only GENT (15 +/- 1 mg/dl and 5.5 +/- 0.6 ml/[min.kg]). MIDP did not affect renal function (BUN, 16 +/- 3 mg/dl; creatinine clearance, 6.1 +/- 1.0 ml/[min.kg]). Light microscopic examination of renal tissue from MIDP-treated rats did not reveal any evidence of cell degeneration or necrosis. Rats given GENT alone excreted 72 +/- 4% of the dose in 24 h and had plasma gentamicin levels of 19 +/- 2 ng/ml 24 h after injection. The group pretreated with DDP had lower urinary GENT excretion (31 +/- 10%) and higher plasma GENT levels (7491 +/- 3750 ng/ml). MIDP pretreatment had no effect on GENT excretion (72 +/- 8%) or plasma GENT levels (16 +/- 2 ng/ml). Thus, MIDP did not cause any measureable decrease in renal function or GENT excretion in our study. Since nephrotoxicity is a significant problem with DDP administration, further studies with MIDP are warranted.

A comparison of the effects of tetraplatin and cisplatin on renal function and gentamicin pharmacology in rats.

Tetraplatin (tetrachloro[d,l-trans]1,2-diaminocyclohexane platinum IV (TTP)) is a new platinum analogue active against L1210 murine leukemia that is resistant to cisplatin (diamminedichloroplatinum II (DDP)). Since nephrotoxicity is a significant problem with DDP therapy, we compared the effects of equitherapeutic doses of TTP and DDP on renal structure and function in rats. We also studied the effects of the 2 platinum compounds on the distribution and excretion of gentamicin (GENT), an antibiotic that is excreted solely by the kidneys. Rats treated intravenously with 2.85 mg/kg of DDP on days 1, 5 and 9 had significantly different plasma urea nitrogen (BUN) levels and creatinine clearance rates on day 16 than those given the same doses of TTP. The renal function of TTP-treated rats did not differ from that of controls or rats given only GENT. Twenty-four hours after a single GENT dose (given on day 15), DDP-treated rats had higher GENT concentrations in the plasma, liver and spleen than rats given GENT alone. TTP-treated rats had higher GENT levels only in the spleen. DDP-treated rats retained a higher percentage of the injected platinum in the renal cortex than those treated with TTP. Light microscopic examination of renal tissue showed necrotic cells and dilated tubules in the proximal tubules of DDP-treated rats while the kidneys of TTP-treated rats were largely indistinguishable from those of controls. Thus, our results indicate that the distribution of platinum in the kidneys differs between rats treated with TTP and those treated with DDP. This may partly explain the considerably lower nephrotoxicity of TTP.