Klaus Muller

Effects of short‐term treatment with the bisphosphonates zoledronate and pamidronate on rat bone: A comparative histomorphometric study on the cancellous bone formed before, during, and after treatment

To study the anti‐resorptive effects of zoledronate and pamidronate on growing long bones we have performed a histomorphometric analysis of the three regions of the proximal tibial cancellous bone of bone formed before, during, and after drug treatment. Male rats (190–220 g) were treated subcutaneously for 10 days with zoledronate (0.028–2.8 μg/kg) or pamidronate (3.7–370 μg/kg) and sacrificed 5 days later. To delineate the three regions of cancellous bone, and for dynamic bone histomorphometry, calcein and demeclocycline were injected at various times. Both bisphosphonates caused a dose‐dependent suppression of cancellous bone turnover and resorption to produce an increase in cancellous bone, but zoledronate was 100 times more potent than pamidronate. The increase in the bone amount and connectivity was more pronounced in the bone formed during treatment where transient bone resorption and normal bone formation led to a positive bone balance. In the bone formed before treatment, inhibition of bone resorption associated with reduced bone formation produced a net gain in amount of bone. Although both bone regions showed a positive bone balance, more bone accumulated in the bone formed during treatment probably because its trabecular bone surface was three times greater. In the primary spongiosa formed after treatment, a moderate increase in the bone amount and connectivity was observed only at the highest dose of both bisphosphonates. The bone formed before, during, and after treatment with bisphosphonates responds differently due to differences in bone architecture, rates of modeling and remodeling, and period of drug exposure. Anat. Rec. 249:458–468, 1997.

In vivo and in vitro Studies on Endothelial Regeneration

Endothelial regeneration was studied in rabbit aorta after intra-arterial balloon catheterization. Most of the regenerated endothelium originated from existing branches which was assessed by the Evans-blue uptake pattern and confirmed by transmission and scanning electron microscopy. Glucocorticoid treatment enhanced re-endothelialization whereas hyperlipemic diet inhibited. Sera from minipigs fed an atherogenic diet consistently have less ability than sera from control pigs to stimulate in vitro the regeneration of wounded endothelium-like monolayers of 3T3-B cells. The deficiency is probably due to an inhibitor which appears and disappears with changes in the diet.

Sequential treatment of osteopenic ovariectomized rats with parathyroid hormone (1-34) fragment and pamidronate

Low doses of PTH(1-34) stimulate bone formation in rats but the effect is reversed after PTH withdrawal. This study shows that this reversal is prevented when sequential PTH-APD treatment is employed. Seventy 3-month-old female wistar rats were ovariectomized, and fed with regular rodent chow and water ad libitum. Twelve weeks later they were divided into seven groups and treated as follows: G1: 3w PTH (5d/w, 20µg/kg/d sc). G2: 3w saline (5d/w, sc). G3: 1w ADP (5d/w, 250µg/kg/d sc) → 3w PTH. G4: 1w APD → 3w saline. G5: 3w PTH → 5d APD → 3w untreated. G6: 3w PTH → 5d saline → 3w untreated. G7: 3w saline → 5d saline → 3w untreated. Two tetracycline labels (2 weeks apart) were administered to each rat before killing. Static and dynamic bone histomorphometries were performed on trichrome stained and unstained sections of distal femoral metaphysis. Cancellous bone volume (Cn.BV/TV) results showed that, when compared with the osteopenic controls (G2, G7), PTH stimulated bone formation (G1) but the effect was reversed after drug withdrawal (G6) and that APD post-treatment prevented this reversal (G5). The results also showed that APD pre-treatment (G3) was as effective as APD post-treatment (G5) in building up cancellous bone, but APD alone (G4) was significantly less effective. Mineral apposition rates (MAR) showed that while APD suppressed bone formation (G4, G5), PTH was able to stimulate bone formation even after APD treatment (G3).

Plasminogen Activator Activity in the Aorta of Strains of Rats with Genetically Determined Different Patterns of Lipids in the Blood

In a strain of genetically hypercholesterolemic rats (RICO), developed from an albino mutant of Rattus norvegicus (Sprague-Dawley, Tif: RAIf, SPF) by selective breeding, the intimal plasminogen activator activity (PAA) at the nonbranching regions of the aorta was markedly lower than at the nonbranching regions of the aorta in the control strain (Sprague-Dawley). At the branching regions of the aorta the intimal PAA showed no difference between the two strains of rats. In another strain of rats (HBC; hyper-beta-cholesterolemic) with a slightly elevated level of total cholesterol in the blood, a high concentration of LDL-cholesterol and a low concentration of triglycerides, the intimal PAA showed no difference from that in the control strain (Sprague-Dawley) at the branching and nonbranching regions of the aorta. 6 weeks after a single injection of streptozotocin at a diabetogenic dose (45 mg/kg) into RICO rats and the control strain, the intimal PAA was found to be increased by 280% in RICO rats, but only by 140% in controls, compared to that in the corresponding nontreated rats.

Effects of Various Hypolipidemic Drugs on Fatty Acid Composition of Liver and Serum Lipids

1. Treatment of rats with hypolipidemic drugs elicited an increase in oleic and a decrease in linoleic acid content in cholesterol esters, triglycerides and phospholipids of serum and liver lipids. 2. The change was most pronounced in triglycerides followed by cholesterol esters and phospholipids. 3. The shift was dose-dependent, starting with doses eliciting hypolipidemic effects. 4. The shift became obvious immediately after beginning of treatment and reached after 4 days a new steady state. 5. This effect was shared by both drugs of aryloxy fatty acid structure, but was not seen with either L-thyroxine or nicotinic acid. 6. The mechanism underlying this phenomenon is thus far unknown, but in our view it merits further attention.