The activities of menthol and peppermint oil were determined in guineapig ileal smooth muscle, in rat and guinea-pig atrial and papillary muscle, in rat brain synaptosomes and in chick retinal neurones by pharmacological 45Ca2+ uptake and radioligand binding assays. Menthol is a major constituent of peppermint oil and is approximately twice as potent as peppermint oil as an lnhibitor of K+ depolarization-induced and electrically stimulated responses in ileum and electrically stimulated atrial and papillary muscles. IC,, values in the ileal preparation ranged from 7.7 to 28.1 pg ml-' and in the cardiac preparations from 10.1 to 68.5 pg ml-I.Similar potencies were demonstrated against K+ depolarizationinduced "Ca2+ uptake in synaptosomes and against K+ depolarization and Bay K 8644-induced uptake in chick retinal neurons. IC,, values for menthol inhibition of K+ and Bay K 8644 responses in the retinal neurons were 1.1 x M (26.6 pg ml-I), respectively, and for peppermint oil were 20.3 and 41.7 pg ml-'respectively. Both menthol and peppermint oil inhibited specific M (17.2 pg ml-') and 1.75 x

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Summary:The most consistent effects of 0.2 mM L-ascorbate on monolayer cultures of rabbit articular chondrocytes were a diversion of incorporated radiosulfate into a pericellular matrix and enhancement of cell proliferation. Only with certain batches of fetal bovine serum (FBS) was there a cell-for-cell increase of proteoglycan synthesis. These actions increased as the cell inoculum rose from 0.5 to 2 x lo5 cells/T25 flask. Maximal effects of ascorbate and D-isoascorbate were found over a range of 0.05-0.2 mM. L-Dehydroascorbic acid was less effective than either, and no stimulatory action was exerted by L-cysteine, glutathione, dithiothreitol, rnethylene blue, or phenazine rnethosulfate. Ascorbate increased the hypro:pro ratio of newly synthesized proteins. p-Aminopropionitrile (1 mM) reduced the proportion of [3Hlhydroxy-proline and [35S]0,-proteoglycans in the ascorbate-supplemented matrix 3 1 and 7%, respectively. In corresponding electronmicrographs, the number of pericellular filaments was reduced. We conclude: (a) Ascorbate has a general anabolic effect on chondrocytes in culture and enhances matrix assembly through mechanisms other than its redox function; (b) deposition of proteoglycans in the matrix is not simply the result of mechanical entrapment by allysine-or hydroxyallysine-derived cross-linking of collagen; and (c) contradictory reports on the subject result from variations in the serum employed, inoculum density, and concentration of ascorbate. Key Words: Ascorbate-paminopropionitrile-Cell culture-Chondrocyte-Differentiation.Several quite contradictory reports describe the effect of ascorbate on proteoglycan synthesis by chondrocytes in culture. The older literature was reviewed by Jouis and co-workers (20). Most articles indicated that ascorbate does not promote proteoglycan synthesis or increases it only transiently (17) and sometimes depresses it (51). In contrast, we (23,29,40,52) and others (9,46) found that ascorbate increases radiosulfate incorporation in vitro. This is one of several anabolic actions of ascorbate. The mechanism involved in the deposition of the matrix has not been established. This article examines sources of the disparities in the literature, documents the specificity of the ascorbate action, and presents data relevant to the prevailing hypothesis that entrapment Of proteoglycan by tightly cross-linked collagen is the basis

To determine the influence of thyroid hormone on beta-adrenoceptors and Ca2+ channels, rats were treated with thyroxine (75 micrograms/100 g sc daily for 5 days) or propylthiouracil (0.05% in drinking water for 30 days). beta-Adrenoceptor density in ventricular tissue, measured by [125I]iodocyanopindolol binding, was significantly increased and decreased respectively, following thyroxine or propylthiouracil treatment to 124.7 +/- 7.11 fmol/mg protein and 71.98 +/- 5.37 fmol/mg protein from euthyroid (control) levels of 93.7 +/- 4.58 fmol/mg protein. Ca2+ channel density, measured by [3H]nitrendipine binding, was altered in the opposite direction; it was significantly decreased and increased to 324 +/- 24 fmol/mg protein and 691 +/- 31 fmol/mg protein from 562 +/- 35 fmol/mg protein after thyroxine or propylthiouracil treatment, respectively. No changes in affinity of either ligand were observed. Responses of isolated papillary muscles from propylthiouracil-treated animals accorded with changes seen in the binding studies. The geometric mean EC50 of isoproterenol increased from 9.5 x 10(-9) mol/l to 5.5 x 10(-8) mol/l, and the EC50 for calcium decreased from 3.16 x 10(-3) mol/l to 1.36 x 10(-3) mol/l; moreover, the responsiveness to the Ca2+ channel activator Bay K 8644 was increased. The corresponding responses in thyroxine-treated animals could not be examined because of prominent arrhythmic activity. As with papillary muscles the sensitivity of left atria to isoproterenol was decreased after treatment with propylthiouracil, with geometric mean EC50 values increasing from 3.21 x 10(-9) mol/l to 89.4 x 10(-9) mol/l.(ABSTRACT TRUNCATED AT 250 WORDS)