2000 1800 1600 1400 '"" ""0 c 1200 5 c. '0 ~ 1000 c ill :J ~ 800 t- 600 400 200 o~--~--~--~--~--~--~--~ 69 70 71 72 73 74 Year Removals of marihuana by USA federal authorities (domestic and foreign cooperative). (In order to roughly estimate the amounts consumed, the amounts removed are usually multiplied by six.) From ""Hearings of the U.S. Senate Committee on the Judiciary (Subcommittee on Internal Security): Marihuana-Hashish Epidemic, Part II, The Continuing Escalation, May 8, 1975,"" U.S. Government Printing Office, Washington, D.C., 1975. then indicated that accumulation of these foreign.
There is much evidence to suggest that prostaglandins may have a physiological role to play in the control of thyroid gland metabolism, although the precise nature of this role remains to be defined. Prostaglandins have been found in normal thyroid tissue, and there is evidence of increased levels in some, but not all, cases of medullary carcinoma of the thyroid. which may account for the associated diarrhea. Exogenous prostaglandins, like TSH, bind to thyroid plasma mem branes, stimulate the adenylate cyclase-cyclic AMP system, thyroid hormone secretion, iodide organification, colloid droplet formation, glucose oxidation, and 32p incorporation into phospholipids. Prosta glandins of the E series are the most potent, although their maximal effects are generally less than the maximal effects of TSH. The interrelationships existing between TSH and prostaglandins have been the subject of intensive investigation, but as yet no one uni fying concept has emerged. TSH and prostaglandins have been shown to occupy different receptors on the thyroid plasma membrane. Al though TSH can increase intracellular prostaglandin levels, probably as a result of increased synthesis, prostaglandins do not appear to be essential intermediates in TSH action on adenylate cyclase. The pos sibility that prostaglandins are part of a negative feedback system con trolling TSH action is, as yet, a tentative hypothesis, and further work will be required to unravel the interrelationships between these sub stances that now appear to be far more complex than has been envisaged thus far.
Arachidonic acid metabolites are known to playa regulatory role in a number of biological systems, in which they function as microenviron mental hormones and intracellular signal mediators. One of the most exciting areas of research of these compounds is the one that studies the relationship between prostaglandins and tumor cell growth and function. In the last few years there has been an extraordinary evolution of data on prostaglandins (and related compounds) and cancer. This vol ume is based on papers presented at the 1986 International Confer ence on Prostaglandins and Cancer organized by the Italian National Research Council and the II University of Rome, and held in Rome, Italy, in June, 1986. This Conference brought together oncologists and specialists in the areas of prostaglandin chemistry, biochemistry, pharmacology, physiology, cellular and molecular biology to overview the actual state of knowledge on the role of eicosanoids in cancer and to focus on the key questions that need to be answered. The picture that comes out of this book describes a very complicated network of interactions between arachidonic acid metabolites and different as pects of the complex phenomenon "cancer". Eicosanoids participate in carcinogenesis initiation and promotion, and their relationship with tumor promoters and growth factors is well established. During cancer growth, different prostaglandins can have different roles in the regulation of cell proliferation and differentiation and in metastasis formation; meanwhile evidence is accumulating for a pos sible use of some of these compounds as antineoplastic agents.
