Role of thymulin on the somatotropic axis in vivo.
OBJECTIVE
There is clear evidence for the existence of a bi-directional thymus-somatotropic axis and several studies suggest that the thymic peptide thymulin may be involved in this communication. We undertook to assess the impact of serum thymulin immunoneutralization in C57BL/6 mice and that of neonatal thymulin gene therapy (NTGT) in nude mice on body weight (BW) gain and on the histomorphometric profile of the somatotrope population.


METHODS
Immunoneutralization of thymulin was done from postnatal day 1 to 35 by i.p. injections of rabbit anti-thymulin serum (α-FTS) and normal rabbit serum (NRS) in controls. NTGT was implemented in nudes using an adenoviral vector expressing a synthetic gene for thymulin (RAd-FTS). On postnatal day 1, heterozygous (nu/+) and homozygous (nu/nu) pups received a single bilateral i.m. injection either RAd-FTS or RAd-GFP (a control vector expressing green fluorescent protein). BW gain was recorded and at the end of the study the pituitaries were immunostained for growth hormone (GH). Serum GH and thymulin were determined by radioimmunoassay and bioassay, respectively.


RESULTS
Thymulin immunoneutralization induced a significant decrease in BW gain, serum GH and somatotrope cell density as well as an increase in somatotrope cell size. NTGT markedly increased BW gain, serum thymulin (P<0.01) and somatotrope cell and volume density in nu/nu mice.


CONCLUSIONS
Our results suggest that thymulin plays a relevant physiological role on the thymus-somatotropic axis in mice.
Department of Cytology, Histology & Embryology B, Faculty of Medicine, University of La Plata, Argentina. preggiani@fcm.uncu.edu.ar
Paula C
PC
Reggiani
Eliana V
EV
Martines
Gisela A
GA
Camihort
Brenda
B
Poch
Rodolfo G
RG
Goya
Gloria M
GM
Cónsole
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D002452:Cell Count; D048429:Cell Size; D005260:Female; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors; D013006:Growth Hormone / Q000097:blood*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008819:Mice, Nude; D011817:Rabbits; D011863:Radioimmunoassay; D013935:Thymic Factor, Circulating / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D013950:Thymus Gland / Q000378:metabolism*; D015430:Weight Gain
D013006:Growth Hormone; D013935:Thymic Factor, Circulating