We examined how pulsatile stimulation with adenylate cyclase-activating
polypeptide 1 (
ADCYAP1) affected
gonadotrophs. In static culture,
gonadotropin-releasing hormone (
GnRH) stimulated transcription of all the
gonadotropin subunits. In contrast,
ADCYAP1 increased common alpha-glycoprotein
subunit gene (
Cga)
promoter activity but failed to increase
luteinizing hormone beta (Lhb) and
follicle-stimulating hormone beta (Fshb)
promoters.
Messenger RNAs for Lhb and Fshb were slightly but significantly increased by
ADCYAP1 stimulation. The results of cotreatment of the cells with
GnRH and
ADCYAP1 was not different from the effects of
GnRH alone on Lhb and Fshb
transcriptional activities as well as on
mRNA expressions. To determine the effect of pulsatile
ADCYAP1 stimulation on
gonadotropin subunit gene expression, perifused LbetaT2 cells were stimulated either at
high frequency (5-min
ADCYAP1 pulse every 30 min) or at
low frequency (5-min
ADCYAP1 pulse every 120 min).
High-frequency ADCYAP1 pulses preferentially increased Lhb
gene expression 2.29-fold +/- 0.15-fold, and
low frequency pulses resulted in a 1.55-fold +/- 0.16-fold increase. Fshb
gene expression was increased 1.87-fold +/- 0.3-fold by
high-frequency ADCYAP1 pulses and 4.3-fold +/- 0.29-fold by low-frequency
pulses. These results were similar to the frequency-specific effects of pulsatile
GnRH.
Follistatin (Fst)
gene expression was specifically increased by
high-frequency GnRH pulses.
High-frequency ADCYAP1 pulses increased Fst to a larger extent (4.7-fold +/- 0.57-fold) than did low-frequency
pulse (2.72-fold +/- 1.09-fold).
ADCYAP1 receptor gene (Adcyap1r) expression was increased significantly following pulsatile
GnRH regardless of
pulse frequency. Low-frequency
ADCYAP1 pulses, however, increased Adcyap1r expression (16.49-fold +/- 8.41-fold) to a larger extent than
high frequency pulses did. In addition,
high-frequency ADCYAP1 pulses specifically increased Gnrhr (
GnRH receptor) expression by 4.38-fold +/- 0.81-fold; however, low-frequency
pulses did not result in an increase. These results suggest that
ADCYAP1, like
GnRH, specifically regulates Lhb and Fshb
subunit gene in a
pulse frequency-specific manner. This regulation may involve alteration in numbers of
GnRH and
ADCYAP1 receptors as well as FST expression.
