SWEET TASTE PERCEPTION FOR PHENYLTHIOUREA (P. T. C.)

HE observation by Fox (1931) that phenylthiourea (phenylthio-T carbamide) was tasteless to some persons while most people tasted the compound as bitter was followed by a genetic analysis by BLAKESLEE and SALMON (1931).Their findings suggested an autosomal recessive mode of inheritance for taste blindness to P. T. C. BLAKESLEE (1932) observed that some persons described the taste of P. T. C. by some term other than bitter, including sour and sweet.RICHTER and CLISBY (1941) reported that among 261 persons 15 (5.75 %) described subliminal solutions of P. T. C. as sweet.Likewise HARRIS and KALMUS (1949) remarked that some persons cha;*acterized P. T. C. as sweet, sour, salty, for example; this particularly so near the taste thresholds of these persons.Examining Japaneses with P. T. C. powder CHIKAUCHI (1952) noted that a few persons found the taste sweet or salty.LUGG (1955) found 3 Malayan Negritos to describe weak solutions of P. T. C. as sour; one of these persons tasted solution 14 (HARRIS' and KALMUS' denomination, 1949) as sweet.In their research series LUGG and WHYTE (1955) noted, among other exceptional taste qualities for P. T. C., sweet taste for this substance in 0 to 2 per cent of the Europeans and Asians.Of 50 Senois in Malaya 8 per cent tasted P. T. C. as sweet at or close to their taste threshold (LUGG 1957). DAS (1958)reported from Calcutta that non-bitter tasters for P. T. C. might not exceed 1 to 2 per cent of the population.He suggested that it might be useful to record such abnormal tasters in various populations and to take up the question of inheritance of such variations by means of family studies.In agreement with this view the frequency of sweet tasters for P. T. C. has been investigated among adolescents in South Sweden, and family data on such sweet tasters have been collected. GUNNAR SKUDE MaterialThe material consisted of grammar or high-school pupils in Malmo.Sweden, of these, 816 were boys aged 14 to 21, mean age 16.7 k 1.5 (S.D.) years and 666 girls, aged 14 to 20, mean age 16.2 k 1.2 years.The overall mean age of the pupils was 16.5k 1.4 years, The parents and sibs of sweet tasters were visited at home and, when possible, examined, 74 % cooperated.Method P. T. C. solutions were prepared in accordance with HARRIS and KALMUS (1949) but with distilled water instead of boiled tap water.Their method implies that from a stock solution, containing 1300 mg.P. T. C. per litre solution, additional solutions are prepared by diluting by, ' / , , I/., etc.The solutions were numbered 1-13, 1 for the stock solution and 13 for the most dilute solution.I used separate beakers made of paraffined paper for each solution.All solutions were kept at room temperature.In the first stage of the study each pupil was tested with solution 10, non-tasters or non-bitter tasters for this solution were tested with solution 7. Any non-tasters or non-bitter tasters of solution 7 were then tested with solution I. Examination with a wider variety of solutions would have interfered too much with their lessons.The second stage of the investigation comprised the sweet tasters secured in this way as well as their parents and sibs.They were tested with a complete series of F. T. C. solutions and with the battery of 7 compounds listed in Table 1.TABLE I. Soiutions used for examination of sweet tasters and members of their families.Compound Dulcine Sucrose Quinine sulphate Strychnine Allylthiourea Hydrocloric acid Sodium chloride Solution n 0.00085 % 0.1 7 0 0.00005 % o.oooo0O4 yi 0.000586 % 0.0015 N 0.04 y7 Solution b 0.00170 % 0.2 % o.Ooo10 % 0.0000008 "/o 0.001172 % 0.0030 N 0.08 % Solutlon c 0.01700 % 2.0 % 0.00100 yo 0.0000080 % 0.011720 70 0.0300 N 0.80 %As indicated in the table, solutions b were twice as concentrated as solutions a, and solutions c were ten times the concentration of b.These

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