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The new cyclosporin (CsA) formulation, Neoral, has different pharmacokinetics compared with Sandimmune (SIM). Larger area under the curve (AUC) values with equivalent trough blood values are reached when Neoral is administered at equivalent doses to SIM. Previously, we showed a great diagnostic reliability when using cytofluorometric analysis from fine-needle aspiration biopsy (FNAB) samples. We investigated possible changes brought about by Neoral on lymphocyte subsets and the repercussions on the activation score cut-off for acute rejection, defined under SIM treatment.

The present work has examined the effects of short‐ (30 min) and long‐term (14 h) exposure to cyclosporine A (CsA) on the uptake of L‐DOPA, its decarboxylation to dopamine and the cellular extrusion of taken up L‐DOPA and of newly‐formed amine in monolayers of LLC‐PK1cells.In the presence of benserazide (50 μM), L‐DOPA was rapidly accumulated in LLC‐PK1cells (cultured in collagen‐treated plastic) attaining equilibrium at 30 min of incubation. Non‐linear analysis of the saturation curves revealed a Kmof 113±16 μMand a Vmaxof 5581±297 pmol mg−1protein 6 min−1.In the absence of benserazide, LLC‐PK1cells incubated with increasing concentrations of L‐DOPA (10 to 500 μM) for 6 min accumulate newly‐formed dopamine by a saturable process with apparent Kmand Vmaxvalues of 31±6 μMand 1793±91 pmol mg−1protein 6 min−1, respectively. The fractional outflow of newly‐formed dopamine was found to be 20%. Up to 200 μMof intracellular newly‐formed dopamine, the outward transfer of the amine was found to be a non‐saturable process.Short‐term exposure to CsA (0.3, 1.0 and 3.0 μg ml−1) was found not to change the intracellular concentrations of newly‐formed dopamine, but increased the levels of dopamine in the incubation medium (143% to 224% increase) and the total amount of dopamine formed (31% to 59% increase). Long‐term exposure to CsA (0.03 to 3.0 μg ml−1) reduced the total amount of dopamine (15% to 39% reduction) and the intracellular levels of the amine (11% to 56% reduction), without changing dopamine levels in the incubation medium. Both short‐ and long‐term exposure to CsA resulted in a concentration‐dependent increase in the fractional outflow of newly‐formed dopamine.Short‐term exposure to CsA (3.0 μg ml−1) reduced the apical extrusion of intracellular L‐DOPA by 15% (P<0.05), whereas long‐term exposure to CsA reverted this effect and decreased its intracellular availability (15% reduction; P<0.05).Detection of P‐glycoprotein activity was carried out by measuring verapamil‐ or UIC2‐sensitive rhodamine 123 accumulation. Both UIC2 (3 μg ml−1) and verapamil (25 μM) significantly increased the accumulation of rhodamine 123 in LLC‐PK1cells. A 30 min exposure to CsA was found not to affect the accumulation of rhodamine 123 in the presence of verapamil (25 μM), whereas a 14 h exposure to CsA was found to reduce the accumulation of rhodamine 123.In conclusion, the increase and the reduction in the formation of dopamine after short‐ and long‐term exposure to CsA, respectively, correlate with the effects of the immunosuppressant on the apical cell extrusion of taken up L‐DOPA, suggesting the involvement of P‐glycoprotein. The effects of CsA on the fractional outflow of newly‐formed dopamine appear to be mediated by a different mechanism.

The accumulation of Ldopa, dopamine (DA) and 3,4-dihydroxyphenylacetic (DOPAC) in kidney slices loaded with Ldopa (10-100 microM) was found to be dependent on the concentration of sodium in the medium (0-160 mM). The constant rate of accumulation did not depend on the concentration of Ldopa used and was about 0.0025, 0.0035 and 0.0065 for Ldopa, DA and DOPAC, respectively. In experiments performed in the presence of 120 and 160 mM sodium, but not with 20 mM sodium in the medium, ouabain (500 and 1000 microM) and amphotericin B (10 and 50 micrograms/ml) significantly reduced the accumulation of both DA and DOPAC (6-21 and 29-56% reduction, respectively). Amiloride (5-100 microM) produced an increase in the accumulation of DA and drastically reduced the formation of DOPAC. This effect was found to be due to inhibition of monoamine oxidase. During monoamine oxidase inhibition ethylisopropylamiloride (1, 5 and 10 microM), but not amiloride (10 and 50 microM), increased the accumulation of newly formed DA in kidney slices and reduced the outflow of the amine into the incubation medium. In conclusion, the results presented here show that the formation of DA in kidney slices loaded with Ldopa is dependent on the concentration of sodium in the medium and sensitive to the inhibition of the enzyme Na(+)-K+ adenosine triphosphatase and activation of mechanisms which bypass the tubular transport of sodium.

Renal artery occlusion (RAO) for 30, 60 or 90 sec was found to reduce norepinephrine tissue levels in both the cortex and medulla of the rat, respectively, by 2 to 5%, 56 to 65% and 92 to 97%, but no significant change in dopamine tissue levels was found to occur. Similar effects were obtained with occlusion of the aorta proximally to the renal arteries for 90 sec. Administration of superoxide dismutase (40 mg/kg) immediately before RAO resulted in a marked protection of the norepinephrine depletion effect as caused by transient ischemia. The sodium-dependent formation of dopamine and 3,4-dihydroxyphenylacetic acid, the deaminated metabolite of dopamine, in renal slices loaded with L-3,4-dihydroxyphenylalanine (50 microM) was found to be similar in denervated and control kidneys. Type A and B monoamine oxidase activities were measured with the deamination of two specific substrates, respectively, [3H]-5-hydroxytryptamine and [14C]-beta-phenylethylamine, in homogenates of the renal cortex and renal medulla; neither type of monoamine oxidase, A or B, was found to be affected by denervation. The renal tissues collected for morphological observation were those in which RAO was performed for 90 sec. The general structure of the renal cortex was not affected by RAO, being similar in the control and the denervated kidney. In conclusion, the results presented suggest that the tissue damaging effect produced by RAO appears to be selective for the renal sympathetic innervation and seems to involve the generation of some reactive oxygen species, namely superoxide.