Objective-To clone segments of the canine liver alkaline phosphatase (LALP) and corticosteroidinduced alkaline phosphatase (CIALP) genes and use those clones to determine the tissue source of CIALP, the kinetics of LALP and CIALP mRNA expression for glucocorticoid-treated dogs, and the correlation between LALP and CIALP transcript concentrations and isoenzyme activities. Sample Population-Tissues obtained from 7 dogs treated with prednisone (1 mg/kg, SC, q 24 h) for up to 32 days and 1 untreated (control) dog. Procedure-Gene segments of LALP and CIALP were obtained by reverse transcription-polymerase chain reaction (RT-PCR) assay. The tissue source of CIALP and IALP mRNA was determined by northern blot analysis of tissues from 1 of the glucocorticoidtreated dogs. Hepatic tissues and serum samples were obtained from the 6 remaining glucocorticoidtreated dogs on days 0, 2, 5, 10, and 32 of prednisone treatment, and relative expression of LALP and CIALP mRNA was correlated with LALP and CIALP activity. Results-A 2,246-base pair (bp) segment of canine LALP and a 1,338-bp segment of CIALP were cloned. Northern blot analysis revealed CIALP mRNA expression in hepatic tissues only after glucocorticoid treatment. Kinetics of LALP and CIALP mRNA expression in the liver of glucocorticoid-treated dogs paralleled liver and serum activities of LALP and CIALP. Conclusions and Clinical Relevance-The liver is the most likely source for CIALP in dogs. Analysis of kinetics of serum and hepatic LALP and CIALP mRNA suggests that after glucocorticoid treatment, both are regulated by modification of mRNA transcript concentrations, possibly through differing mechanisms.

Objective-To determine the effect of glucocorticoids on the induction of alkaline phosphatase (ALP) isoenzymes in the liver, kidneys, and intestinal mucosa, 3 tissues that are principally responsible for ALP synthesis in dogs. Sample Population-Tissues from the liver, kidneys, and intestinal mucosa of 6 dogs treated with 1 mg of prednisone/kg/d for 32 days and 6 untreated control dogs. Procedure-Using canine-specific primers for the ALP isoenzymes, a reverse transcription-polymerase chain reaction assay was designed to measure liver ALP (LALP) and intestinal ALP (IALP) mRNA and heterogeneous nuclear RNA (hnRNA) expression in tissues from the liver and kidneys and intestinal mucosa of glucocorticoid-treated and control dogs. Tissue ALP isoenzyme activities were compared between the groups. Results-The LALP activity and mRNA concentrations increased in tissues of the liver and kidneys in dogs treated with prednisone, whereas LALP hnRNA increased only in liver tissues. The IALP activity and mRNA expression increased in intestinal mucosa and liver tissues in prednisone-treated dogs. We did not detect an increase in IALP hnRNA expression in these tissues. Conclusions and Clinical Relevance-Synthesis of ALP is increased in the liver, kidneys, and intestinal mucosa of dogs in response to prednisone treatment. This response appears to be regulated at the transcriptional level, but mechanisms may differ between LALP and IALP.