Smooth muscle cells were grown from thoracic aortas of rats. The effect of insulin on the proliferation of these cells was studied by comparing the growth of cells in culture medium containing insulin and 1% fetal calf serum with growth of cells in culture medium containing only 1% serum and in culture medium containing 10% serum. Insulin in concentrations of 10, 50, 100, 1000 and 10 000 microunits/ml induced smooth muscle cells to stationary growth more rapidly than basal medium. This could be demonstrated as well in the logarithmic growth as in confluent cells grown in medium with 1% serum. However, the highest concentration of insulin did not stimulate growth to the same degree as medium containing 10% serum. Cells that were older in culture life (11th passage) did not show a growth response to insulin.
The effects of dexfenfluramine on 24-hour profiles of ACTH, GH, norepinephrine, insulin and FFA were studied in a group of obese male patients. A controlled comparison trial under metabolic ward conditions was conducted. Dexfenfluramine (15 mg twice daily) was given for 8 days, while patients adhered to a weight maintaining diet. 9 obese patients were treated with dexfenfluramine. 9 obese patients who were randomized on the basis one after another served as a control group. After a 3 day run-in period at 8 am, 10 am, and 4 pm, 8 pm and 12 pm, and 8 am of the following day ACTH, GH, norepinephrine, insulin and FFA were measured before and during the 8th day of dexfenfluramine treatment. During the study body weight slightly decreased in both groups. In the DF group systolic and diastolic blood pressure declined during treatment. The norepinephrine levels were depressed during DF treatment over the entire day. The 24-hour profile of ACTH levels changed in the treatment group to a more distinct circadian rhythm with slightly higher levels in the morning and lower levels at night. The 24-hour profile of GH changed in the drug treated group with a diminished peak of GH secretion at night. Serum concentrations of insulin and FFA were decreased during DF treatment. The hormonal changes during dexfenfluramine treatment suggest that the drug affects endocrine mechanisms that may be involved in regulation of energy balance. Treatment with dexfenfluramine results in decrease of FFA. The mechanisms by which dexfenfluramine operates and displays its various effects on hormones and lipolysis have not been studied.
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