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Growth Responses in Thyroidectomized, Hypophysectomized and Alloxan Diabetic Rats Infected with Plerocercoids of the Tapeworm, Spirometra mansonoides¹

Departments of Biochemistry (WRR), University of Nebraska College of Medicine, Omaha, Nebraska 68105; and Microbiology (JFM), State University of New York Upstate Medical Center at Syracuse, New York 13210

The growth-stimulating effects of plerocercoids of the tapeworm, Spirometra mansonoides were studied in groups of thyroidectomized (Tx), hypophysectomized (hypox) and alloxan-diabetic (AD) rats fed either low fat, digestible carbohydrate-free or basal purified diets. Thyroidectomized-infected rats grew about 3 to 4 times as fast as thyroidectomized control rats and hypophysectomized-plerocercoid-infected rats showed even greater rates of growth as compared to their hypophysectomized controls. Although all surgically prepared rats infected with plerocercoids grew about half as fast as intact noninfected control rats, the infected animals ate only half as much food. Consequently, the food efficiency (g food/g wt gain) of worm-infected animals was essentially the same as that of noninfected control rats. The growth rate of intact weanling rats was not stimulated by plerocercoids and the lack of fat or digestible carbohydrate in the diet had no observable effect on the plerocercoid-induced growth response. The plerocercoid growth factor (PGF) does not contain thyroid hormone activity but it is diffusible through a Millipore filter of 0.22 µ pore size. It is not known whether PGF itself induces growth in Tx, hypox and AD rats or whether it causes the host animal to produce yet another factor that initiates the growth response.

KEY WORDS: • thyroid • tapeworm • Spirometra mansonoides

¹ This study was aided in part by grant AM 13579 from the NIII, U. S. Public Health Service.

Manuscript received 20 April 1973.