PHYSIOLOGY OF ANTERIOR HYPOPHYSIS 



251 



sentation of the aiiiount of gonadotrophins 

 present at the moment of death, is a result- 

 ant of the rate of synthesis and the rate of 

 liberation. Whether such potency measure- 

 ments provide any reasonable clue to the 

 actual rate of secretion has been debated. 

 The significance of such measurements is 

 enhanced by the preponderance of cases 

 in which the potency has correlated well 

 with function, as revealed by the gonads and 

 reproductive tracts of the donors (Meyer, 

 Biddulph and Finerty, 1946; Robinson and 

 Nalbandov, 1951; Kammlade, Welch, Nal- 

 bandov and Norton, 1952; Bahn, Lorenz, 

 Bennett and Albert, 1953a; Greeley and 

 Meyer, 1953; Nalbandov, 1953b, a review; 

 Simpson, van Wagenen and Carter, 1956 j. 

 These correlations, however, were not al- 

 ways close and in a few instances, as noted 

 elsewhere (page 261) , pituitary potency and 

 function diverged sharply. As long ago as 

 1939 Smith surmised that the usefulness of 

 whole gland assays in the study of pituitary 

 physiology had been nearly fulfilled. The 

 prediction seemed reasonable but the tech- 

 nique, with some refinements, is still widely 

 used and is one of the important means 

 of gaining insight concerning the probable 

 level of gonadotrophic function. It would be 

 exceedingly helpful to be able to determine 

 the blood level of the gonadotrophins, but 

 even this would not reflect the rate of entry 

 of the gonadotrophins into the blood stream 

 unless the rate of destruction and excretion 

 were also evaluated. 



For the most part the levels of circulating 

 gonadotrophins in normal animals have 

 been found/to be very low and are generally 

 below the /sensitivity of the available cri- 

 teria for defecting them. Significant gonado- 

 trophic activity has not been found in the 

 blood or urine of ruminants (reviewed by 

 Benson and Cowie, 1957) and the fact has 

 been re-emphasized by the circumstance 

 that no trace of such activity was found in 

 volumes of sheep blood as large as 500 ml. 

 (Bassett, Sew^ell and White, 1955). Normal 

 rat plasma has also yielded consistently 

 negative results except for one unconfirmed 

 report of a trace of LH activity (Hellbaum 

 and Greep, 1943) . The plasma of gonadecto- 

 mized rats, however, like the plasmas of 

 menopausal women or gonadectomized men 

 and women, was early found to contain 



demonstrable gonadotrophic activity (Em- 

 ery, 1932). Later, Hellbaum and Greep 

 (1943) reported finding FSH, but no LH, 

 in 10 ml. plasma from castrated male rats. 

 Recently this result has been confirmed in 

 substance by Cozens and Nelson (1958). 

 Using closely spaced injections, they ad- 

 ministered to hypophysectomized, immature 

 female rats up to 24 or 32 ml. plasma from 

 spayed adult female rats over a 4-day pe- 

 riod ; although they found a clear indication 

 of FSH activity, ICSH was not apparent. 



A. PHYLOGENETIC CONSIDERATIONS 



The end points of cross-species testing 

 of pituitary glands for gonadotrophic po- 

 tency have comprised mainly gonad stimu- 

 lation in immature male and female rats and 

 mice and in 1-day-old male chicks, ovula- 

 tion in estrous rabbits or pregnant mice 

 (Ladman and Runner, 1951), ovulation or 

 spermiation in frogs, and coloration of spar- 

 row bill or Weaver finch feathers. The con- 

 ditions of the assay have varied greatly; 

 the test animals have been of different ages 

 at the start of treatment; they have been 

 hypophysectomized in one study and intact 

 in the next; the dosage has been expressed 

 in integers or fractions of whole glands or 

 as milligrams, wet weight or dry weight, of 

 pituitary tissue. The data often do not per- 

 mit comparisons of assays of pituitaries 

 from a given species, leaving aside the diffi- 

 culties of making interspecies comparisons. 

 The extensive literature on this topic has 

 been reviewed repeatedly (Smith, 1939; van 

 Dyke, 1939; Burrows, 1949; Chester Jones 

 and Eckstein, 1955). 



). Ascidians 



On the basis of tests in three intact 26- 

 day-old mice, Carlisle (1950) claimed to 

 have detected gonadotrophic activity in the 

 neural gland of ascidians. Dodd's (1955) 

 recent evidence of more substantial nature 

 casts doubt on the validity of this claim — 

 yet leaves the question open, since 1 of 

 Dodd's 10 intact 19-day-old mice receiving 

 as much as 230 neural glands each gave a 

 positive response. The further statement by 

 Carlisle (1954) that mammalian pituitary 

 and urinary gonadotrophins promote ovula- 

 tion and sperm discharge in the ascidians 

 has likewise been challenged (Dodd, 19")oi. 



