Occurrence in Fresh-Water Animal s 



Fresh-water animals, in comparison to marine animals, contain 

 little trimethylamine oxide (tables 2 and 3). The mean content of 

 trimethylamine oxide in marine teleosts vas 5^.9^ whereas in fresh-water 

 teleosts it was only 7*5 nig. trimethylamine oxide nitrogen per 100 g. 

 Trimethylamine oxide is not found in fresh-water plants or in fresh-water 

 zoopleinkton (Kapeller-Adler and Verinig 1931) • Dimethyl- and trimethyl- 

 amine are also absent from fresh-water algae, but methylamine is present. 

 Tertiary amines have been reported in a number of land plants (Challinor 

 1911^, Cromwell 1950, Gessner 1950, Guggenheim 1951, Henry and Grindly 19^4-9, 

 Smith and Yoxzng 1953, and Steiner and Stein 195^4-). 



PHYSIOLOGICAL AMD BIOCHSGCAL SIGNIFICANCE 

 OF TRIMETSnAMINE OXIDE 



It is not unreasonable to expect that trimethylamine oxide, which 

 is widely distributed in marine organisms, is associated with some function 

 or functions in these animals. It has, however, been difficult to show 

 these expected relationships. Consideration is given in the following 

 sections to the probably functions of trimethylamine oxide in different 

 animals and to the theories on the origin of the oxide. 



Osmoregulation and Excretion 



Since there are differences in osmoregulation and excretion among 

 the groups of marine and fresh-water animals, the possible relationship of 

 trimethylamine oxide to these functions will be discussed for each group of 

 animals. 



Elasmobranchs . - -The osmotic pressiire of the tissue fluids of the 

 marine elasmobranch is greater than that of sea water or of the urine of 

 these animeds (Baldwin 19li-8, Smith I93I and I936) . A urea content of 2.0 to 

 2.5 percent plus trimethylamine oxide may constitute k2 to 55 percent of the 

 total osmotic pressure of elasmobranch plasma (Cohen, Krupp, and Chidsey 

 1958) . Trimethylamine oxide contributes 7 to 12 percent of this total 

 (Hoppe-Seyler 1930). Although this contribution is smsill, it appears to be 

 important, since renal conservation of the oxide has been shown in elasmo- 

 branchs. The filtered oxide is almost completely reabsorbed in the kidney. 

 Hoppe-Seyler (1930) observed that the concentration of the oxide in the 

 urine was 10 percent, or less, of that in the plasma. The mean concentration 

 of oxide in the plasma for 39 specimens of dogfish was 99 + li; mg. N/lOO ml. 

 Over a 2i4-hour period, this concentration only varied 6 to 9 nig. N/lOO ml. 

 per specimen. This shows that the concentration is controlled over a narrow 

 range (Cohen, Krupp, and Chidsey I958). 



11 



