tokens: The increments in median plasma secretin concentration were 1 . 6 , 3 . 0 , and 6 . 4 pmol x 1 ( - 1 ) after secretin , 125 , 250 and 500 fmol x kg - 1 , and the corresponding 15 - min bicarbonate output 283 , 442 , and 1435 micromol , respectively .