Alkaline phosphatase in serum and tumour of rats bearing a hormone-responsive transplantable osteogenic sarcoma

Serum alkaline phosphatase (AP) levels in rats bearing a hormone-responsive transplantable osteogenic sarcoma correlate closely with the growth of the tumour. Loss of serum AP activity after tumour removal together with data on heat susceptibility of tumour and serum AP provide strong circumstantial evidence that the serum AP is derived from the tumour and is similar to bone isoenzyme. Increased levels of the enzyme were not detectable until the tumour had reached a readily palpable size. Tumour AP production was unaffected by castration or ovariectomy but thyro-parathyroidectomy reduced tumour growth slightly and tumour levels of AP, whilst increasing serum AP as a function of tumour size. A single acute injection of salmon calcitonin into tumour-bearing thyro-parathyroidectomised rats significantly reduced serum AP activity. The tumours of such treated rats had significantly higher AP activity than tumours of similar rats treated with bovine parathyroid hormone.