Forskolin, a plant cardiotonic diterpene, stimulated proteoglycan biosynthesis by chondrocytes in monolayer culture. The quantitative increase in proteoglycans was dependent on the concentration of forskolin, but was relatively independent of the presence of serum. At forskolin concentrations that stimulated proteoglycan synthesis, a significant stimulation of adenylate cyclase and cAMP was also measured. The quantitative increase in proteoglycans was characterized, qualitatively, by an increased deposition of newly synthesized proteoglycan in the cell-associated fraction. An analysis of the most dense proteoglycans (fraction dA1) in the cell-associated fraction showed that more of the proteoglycans eluted in the void volume of a Sepharose CL-2B column, indicating that an increased amount of proteoglycan aggregate was synthesized in forskolin-treated cultures. The proteoglycan monomer dA1D1 secreted into the culture medium of forskolin-stimulated cultures overlapped in hydrodynamic size with that of control cultures, although cultures stimulated with forskolin and phosphodiesterase inhibitors produced even larger proteoglycans. The hydrodynamic size of 35SO4 and 3H-glucosamine-labelled glycosaminoglycans isolated from the dA1D1 fraction of the culture medium was greater in forskolin-treated chondrocytes, especially from those in which phosphodiesterase inhibitors had been added. These results indicated that forskolin, a direct activator of chondrocyte adenylate cyclase mimicked the effects of cAMP analogues on chondrocyte proteoglycan synthesis previously reported. These results implicate activation of adenylate cyclase as a regulatory event in the biosynthesis of cartilage proteoglycans, and more specifically in the production of hydrodynamically larger glycosaminoglycans.

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The anabolic effects of testosterone on kidneys from two strains of female mice were studied over a course of 25 days. The A/J and C57BL/6J strains were selected because they carry regulatory alleles Gura and Gurb which determine rapid and slow induction of β‐glucuronidase, respectively. (A major goal of this study was to determine whether these mouse strains have other differences in their responses to testosterone). The wet weight, dry weight and total protein content of the kidneys of both strains increased about 70% in both strains. Total RNA increased 112% and 93% in a biphasic manner in the A/J and C57BL/6J mouse strains, respectively. The steep slope during the first 5 to 7 days was attributed to a selective stimulation of RNA accumulation while the latter, less rapid, RNA increase occurred in parallel with tissue growth. The total DNA content of kidneys from testosterone treated A/J mice never increased above that of controls, indicating that hypertrophy could account for renal enlargement in this strain. By contrast, testosterone treatment produced a 24% increase in total kidney DNA in C57BL/6J mice, signifying that both hypertrophy and hyperplasia are important factors in the anabolic response of this strain. These observations indicated another difference in the androgen induced response of A/J and C57BL/6J mice. As a consequence of the testosterone stimulated increase in renal β‐glucu‐ronidase synthesis, the excretion of the lysosomal form of the enzyme into the urine increased 2200‐fold in A/J but only 57‐fold in C57BLIGJ. The total enzyme activity excretedidayimouse was only 4 times higher in A/J versus C57BLi6J with the differences reflecting the basal activity which was 10‐fold higher in C57BLIGJ mice. The basal excretion of another lysosomal enzyme, β‐galactosidase, was also several fold higher in C57BL/6J, suggesting that lysosomes in those animals are either larger or their contents are excreted at a faster rate.