DOES THE PITUITARY GLAND AFFECT THE SECRETION OF SEBUM? 403 lation of lipogenesis with the gland prior to any of those events being observed ? Have studies with tritiated thymidine confirmed that DNA replication is stimulated in glands which subsequently show enlargement and renewed sebum secretion? ThE LECTURER: A holocrine gland will increase in size if cells are produced at a greater rate than they are discharged. This whole question of the relationship between cell production, turnover time and gland size is complicated. I think steroids have two effects, an effect on cell division and an effect on lipogenesis within each cell. The evidence for this lies in the differential effects of different steroids. Some will stimulate mitosis more than sebum production and some will stimulate sebum production to a greater extent than mitosis. If oestrogen as well as androgen is administered, the oestrogen has very little effect on cell division but it has a marked effect in inhibiting intracellular synthesis of sebum the result is a gland which produces a lot of cells, but little sebum. To the question whether rat sebaceous glands have been labelled with thymidine, the answer is that this has not been performed by us, nor, as far as I know, by anyone else. DR. D. JAcI•soN: Your technique relies on the extraction of the hair fat from hair clipped from the flank of the rats used. There is some evidence to suggest that hypo- physectomy in particular causes some change in the type of hair produced could you perhaps comment on this with respect to your own work, and in general when con- sidering the effects of a hormonal treatment on enticular appendages. ThE LECTURER: Our hair fat measurements were carried out over a period of only eight days, and although, of course, I agree with you that hypophysectomy does affect the hair, and so will our hormonal treatment, such effects would only be significant over a far longer period. Any change that could take place in the hair during the experiment would not be enough to affect the result materially. MR. K. M. GODFREY: I note that you are subjecting animals to a sodium lauryl sulphate solution and presumably to get the cleansing required you exceed a level which will cause irritation. Are the levels of skin affected by irritation and the gland- ular situations that you are talking about so different, that one will not affect the other, or is there some possibility that irritation caused by your cleansing technique may affect your results? ThE L•CTURER: I do not know. All I can say is that our experiments are adequately controlled in the sense that both the control animals and the steroid treated ones have exactly the same treatment by washing. Our animals do not show any signs of skin irritation by our technique. MR. K. M. GODFREY: Very interesting you say that you see no visual signs of irritation? Tn• LECTURER: We only wash them on two successive days, the first day to get them used to it, and on the following day, before we take the hair sample. They do not seem to mind the performance, and there are no signs of irritation. DR. J. L. BURTON: I wonder whether you have studied the effect of ACTH in

404 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS adrenalectomized animals? This might enable you to determine whether the ACTH acts directly or via adre•al androgens. THE LECTURV. R: XVe have measured sebum production in a few adrenalectomized rats. The experiments were done because we wanted to test the effect of oestrogens. We were trying to settle another controversy, whether oestrogens act peripherally or by suppressing endogenous androgen production. The idea of adrenalectomizing as well as castrating was to remove all possible sources of endogenous androgen produc- tion, so that we had adrenalectomized-castrated control rats, some treated with oestrogen, and some with both testosterone and oestrogen. But we did not have non- adrenalectomized controls to compare with adrenalectomized controls. What I can say, however, is that the levels of sebum production in the adrenalectomized rats appeared somewhat lower than the levels in non-adrenalectomized rats. We have not given ACTH to such animals. I do not know whether any work with adrenalectomized rats has been done at Newcastle, but they are extremely difficult animals to keep alive and handle, and they do tend to die when you give them a bath!