Comparative Studies on the Properties of LATS and TSH

Abstract

LATS activity was neutralized by pretreatment of mice with anti-IgG in vivo. Simultaneous injection of epsilon-amino caproic acid and hydrocortisone does not inhibit LATS action. Human thyroid-microsomal fractions neutralize LATS activity and TSH activity. The decrease in activity of LATS and TSH caused by thyroid microsomes correlates positively. Calf thyroid microsomes are much less active than human thyroid microsomes in absorbing LATS activity. Deoxycholate and sonification solubilize the LATS neutralizing activity. No visible precipitate formed between these solubilized fraction and LATS-IgG, using the Ouchterlony agar diffusion method. LATS did not differ from TSH in heat stability, and partially heat denatured LATS still had a long acting type response. Dissociation of a small rapidly acting molecule from LATS could not be obtained in high molar NaCI solution. LATS-IgG fragments digested by proteolytic enzymes (papain, pepsin, trypsin, and ficin) had a prolonged response like LATS. However, these fragments, in the presence of cysteine, either gave the same response after 2 hr and 8 hr, or gave a short acting response like TSH. The thyroid stimulating active site of the LATS active gamma globulin may be situated in Fab or Fab fragments having the antibody combining site. LATS did not stimulate the chicken thyroid, although TSH had this action. The proteolytic fractions of LATS-IgG also did not stimulate the chicken thyroid. No increase of gammaglobulin and/or IgG was found in some sera with a high LATS activity. Binding of LATS-IgG to mouse or human thyroid could not be visualized using the Coon's immunofluorescent method. These data support the concept that LATS is an IgG having a high specific activity of thyroid stimulating action.

Effect of LATS, TSH and cholera toxin on the thyroid gland in nude mice.

“…Evidence has been accumulated that LATS (Long Acting Thyroid Stimulator) may stimulate the thyroid gland in all mammalian animals (Adams 1958;McKenzie 1958;Lepp and Oliver 1967;Ochi and DeGroot 1970). For bioassay of LATS, the guinea pig or mouse has been used.…”

Thyroid Stimulating Immunoglobulin(TSI) in Graves' Disease.

“…On the other hand, TSAb (without LATS activity) may stimulate the human, bovine and porcine thyroid but not guineapig or mouse. TSH (mammalian species) stimulates the thyroid of all animal species [10,11]. It is suggested that LATS may have thyroid stimulating (TS) activity for lower developed animals (rodents such as guinea-pig, rat and mouse) compared with TSAb (without LATS activity) [11] (Table 1).…”

“…TSH (mammalian species) stimulates the thyroid of all animal species [10,11]. It is suggested that LATS may have thyroid stimulating (TS) activity for lower developed animals (rodents such as guinea-pig, rat and mouse) compared with TSAb (without LATS activity) [11] (Table 1). When TBII (with TSH receptor assay) and TSAb [CAMP production in porcine thyroid cells (PTC) assay] were determined, all LATS positive sera showed extremely high TSAb and TBII activities [12].…”